This video shows how commercial cat food make your cat have tartar?

When i tried Hills pet oral care , it didn't left any residue, which becomes sticky and then stone-tartar like susstance..

natural cat food doesn't left sticky and then stone like substance..

they only decay ,decompose and disappear.

that's why raw food is good to cat's dental health..

am i right?

I don't know if your experiment really proves anything or not, simply because most people do not mix kibble with water, and when a cat eats kibble, it mixes with saliva, not water, in their mouth.  And the kibble does not stay on their teeth, it goes into their stomach.

As for feeding raw, which I do, that does not necessarily clean their teeth.  It's the chewing on bones or large pieces of meat that clean their teeth.  But the bones, mainly.  Unfortunately, not all cats will chew on the bones.  Mine don't.  So far, mine will only eat ground up bones, so they aren't really getting any dental benefit from raw that I have found.  At their last check-up, they still had some tartar build-up

Actually, just eating raw does benefit their oral health. It doesn't mean there won't be plaque, but it should reduce it - because the meat is more acidic than a kibble or canned diet, so a raw diet results in lower level of bacteria build-up in their mouths (and it is the bacteria build-up that causes the plaque/tartar). It's the chewing on the bones that would help remove the build-up.