http://www.learner.org/jnorth/images/graphics/n-r/OceanCurrentsUSNOO.gif A tornado forms when warm and cold currents meet, forming a cyclon which grows till hits the ground. There are times when a tornado starts to form but doesn't meet ground. As you see in the picture, warm and cold currents don't really exist near china... the nearest is Japan. But there are many other places on earth.

Why haven't I seen any tornadoes in China?* Who has ever seen a tornado (here)?/ Has anyone ever seen a tornado (here in China)?* I don't know why though, just helping with the English :]

I am not qualified to explain, but I have experienced tornadoes in the United States. The middle south portion of the US has the right weather conditions for these storms. Be grateful China does not have these.