I read this with rationalism until I got to the point where you shared that you crate them. You shouldn't have pets if you have to crate them. You're a bad pet owner. Not only the crate factor but the fact that you obviously don't understand common traits between animal species that you should have at least a small clue about before getting any animal as a pet. Dogs chase things. It's part of their natural behavior. Both cats and dogs are pack animals. They attempt to establish dominance. A pet owner needs to take control and be the "pack leader" so none of the other animals take and establish dominance as their own. Allowing one pet to be dominant over others, and posessive of things, is bad pet parenting. 

You need to be trained. Note I said you need to be trained. The animals don't need trained, you do. Get a trainer to help you with this situation. It's unfortunate that you don't know enough about them to be able to be successful correcting all of these situations yourself. There's more there than just the dominance and territorial thing. The longer you leave it go because you're ignorant (that's not an insult, please agree and admit that you may not know enough) the worse it's going to get. 

Chows grow to be big, strong, powerful dogs and they do have a tendency to be visious if they're not properly trained and socialized. It will get the cat one of these days and there's really a 80/20 chance with the cat having the better chance the dog will survive if it's not quick enough to kill the cat before it can defend it self. Cats can be extremely wicked, more so than dogs. 

You need a trainer. Or you need to give up the Chow to a better home. 

I don't believe in having cats and dogs. Much of the time thecatis trying to avoid the dog

Probably thought the cat looked delicious 

Why the Hell would you have the Chow on such a long effing leash??? Chows are VERY aggressive dogs and it will likely KILL the cat AND the Pug.

The only dogs chasing cats in a household are those owned by horrible owners that LET them do that.  I have a dog and he has never EVER shown ANY aggression or chased ANY of my cats.  Neither have the two dogs I've had before him.  Stop making excuses for being a horrible, uncaring pet owner.  It's up to YOU to protect your cat.Get rid of the dog.  The cat was there FIRST.

edit: I just read this part.  "Disclaimer: The previous Chow owner had to keep their cats separated from the Chow at all times - they didn't say why, but they said she would chase them and they didn't want to find out what would happen if she caught them, and that's why they gave her up. But knowing how dominating our cat is, we didn't think it would be a problem." Why the F would you bring this dog into your home KNOWING it was cat aggressive?  You are HORRIBLE!!!!!  The fact your cat is "dominating" isn't going to save it.  In fact, it will make it MORE likely to be ripped apart by that dog because it will stand up to it!  You're a MORON!

Honestly, when people like you add such dogs to a home with cats...

That's just grossly irresponsible. WTF?!

To a dog, when one goes over onto one's back, that constitutes a surrender and lets the other know he is being submissive to the other dog. That is where we get the term "Belly up" meaning to surrender or become a coward. To a cat, going onto your back is just freeing up all four claws and the teeth for fighting. So a cat that feels threatened will go onto its back, the dog will think it has a surrender and the dog will move into show its standing as the dominant one. Then the cat attacks and the dog does not know what to do. You are lucky the cat runs away because you could end up with a ripped up dog otherwise.

Chows are not known to be very cat friendly.  If the prior owner had to separate the Chow from their cats, its a good indication that if the chow is loose it WILL go after the cat and possible kill it.  Dog should be rehomed to someone without cats.

And since your Pug is chasing the cat all the time, why would you bring in a 2nd dog to do that same.  You need to teach your Pug to stop chasing the cats.  We have a Jack/Dachshund mix that was chasing our cats.  Finally stopped her by using a water squirt bottle whenever she started bothering the cats.  It worked for us and the cats are much more tolerant towards her now and she has not really chased them for awhile now.

Disclaimer: The previous Chow owner had to keep their cats separated from the Chow at all times - they didn't say why, but they said she would chase them and they didn't want to find out what would happen if she caught them,

This is not a disclaimer. This makes me pray that you are a troll because if you are not, you are either the dumbest least caring person or just the biggest piece of sh it to ever post in the cat's section

It's incredibly dumb to bring home a dog that was being given up because of persistent cat-chasing when you have a cat. Such an accident was bound to occur at some point in time, particularly with the level of obsession the dog had with your cat. When you couldn't stop that behavior pretty immediately, the dog should have been given up at that point. And really, it doesn't matter in the least if the dog was "playing" or intended to kill the cat. A dog that size "playing" with a cat could cause the cat's death.  The inevitable happened, your cat was injured, and you're lucky your cat didn't pay for your poor judgment with her life. Make sure the dog's new home does NOT have a cat in it, and impress upon the new owners the seriousness of keeping her away from cats. 

Over the past four months, we've been trying to introduce them and get them more used to each other, so that the Chow wouldn't always want to get to the cat. We figured if she got used to the cat, eventually she'd stop wanting to chase her. With every interaction, she's been on a leash. Each time, the Chow barks very loud and the cat growls and hisses, and tries to get away. She's obviously scared. 

Going forward, we decided to just keep them on separate floors. The dog stays downstairs, and the cat stays upstairs. The dog is not allowed out of her crate unless all doors upstairs are shut. And the cat is not allowed downstairs unless the dog is locked away. There is a gate at the bottom of the stairs. 90% of the time, the dog sits at the bottom of the stairs waiting for the cat.

On Saturday night (March 7th), I was taking a shower upstairs, and I heard what I thought was a dog running around on the carpet in the hallway (but I couldn't tell if that was the Chow or the Pug - all I heard was the collar tags shaking). My husband was getting dressed in the bathroom, and I said "What's that noise?" and he said it was our Chow Chow and I yelled "Why is she up here???!!!" (she's not allowed upstairs at all). My husband ran after her and found her in our other bathroom, our cat was laying on her back, the Chow had her pinned down, and her mouth was around her stomach. He said he kept trying to pull the Chow off but she wouldn't get off. He said he pulled her, and the cat came up with her. He said he then had to punch our Chow Chow hard to make her drop the cat. I then came out of the shower, and our cat was covered in pee (from being terrified) on my bed and throwing up and breathing fast, and wouldn't let anyone touch her. My husband said we needed to get our cat to the animal hospital ASAP. 

Turns out, my husband asked my daughter to put the Chow in the crate, as we were going out to eat (and she gets crated while we're out), but the Chow got away from my daughter and ran upstairs (Not sure why he asked her to do it in the first place. The Chow is strong!) Unfortunately, our bedroom door was left open, and that's where the cat was.

On the way to the ER, I was crying and we both said that we can't keep the Chow anymore. I posted an ad for her on the classifieds. 

I feel so bad rehoming our Chow (we still have her for the time being), especially since I didn't witness the "attack" happen. How do I know this wasn't just hard "playing"? I know dogs play with their mouths. Or if this was really her trying to KILL my cat? 

Our Chow Chow is litterally the most well behaved dog we have ever had - with the exception of trying to chase our cat. She gets along so great with our Pug. She is also very good with other male dogs, however, she is territorial around female dogs (my cat is also a girl. I wonder if it would be different if she was a boy cat?) Whenever we go to the dog park, or just take her for a walk around our neighborhood, and she sees a female dog, she barks aggressively towards it. She never bites, though. 

Our cat is home now and recovering, but this was too much of a close call for us. 

It's breaking my heart to let go our of Chow Chow. She is super affectionate towards me, my husband, our young kids, and our dog. We will miss her terribly. But if we keep her, and this happens again (or worse, she kills my cat), I would be devastated. 

I couldn't look at our Chow for the first 24hrs after the attack. Last night as I was eating dinner, she was sitting there watching me. :( I stopped and went over and just picked her up and held her and cried. She sat in my lap, licking me constantly with her black tongue. It broke my heart.

TLDR: We kept our cat and Chow Chow separated, on different floors for the past 4 months due to the dog trying to get to the cat. A door was left open, unfortunately, and the dog got to the cat and had her pinned down with her mouth around her stomach. We got to them in time, but still had to take the cat to the ER.

How do I know though, if this is her just wanting to play, or if she actually is trying to kill my cat?

She loves to chase my Pug around, and what if she's just trying to "chase" and catch the cat (not to eat, just to play)?

Anyone with similar experience? Advice?