Is chinese food bad to eat for asthma?

Not all. Some chinese restaurants use msg in their food, which bothers some asthmatics - but not all asthmatics are bothered and many restaurants don't use it anymore. Ask if they use it, and avoid it if they do and won't keep it out of your food. China has 1.2 billion people - not all the food there bothers asthmatics.
No, it is fine. Chinese food is just fine for asthma patients, as long as they are not allergic to something in a particular dish, because food allergies can sometimes cause asthma symptoms. The chinese food, of course, should be prepared in a healthy manner, without much fat nor excess salt. There are over 1 billion chinese people in the world, and they seem to do alright eating their meals.