Well, my first guess would be to stay away from having too much cavalry on the table. If those rockets hit them then they will probably leg it.
The chinese army list is much like the fantasy empire army and should probably be treated with as such. They have pretty steady infantry, some nice cavalry and some tough chariotry. I would stick to a mostly infantry heavy force with skirmishers guarding my flanks and some cavalry, not too much, to press an advantage.
If you can make some big units of infantry charge and automatically break some of his line then you could have some success although their leadership is pretty decent so you won't have the game winning charge that you may against other armies.
You might even want to start a general engagement and then try to head hunt his general if possible. The general seems like the weak link in the armor having only a 3 toughness and being only eligible for a 5+ armor save unless he is in a chariot.
The one thing to keep in mind is that if he does have any rocket artillery then you might want to close as quickly as possible as the closer you get the less likely he is to want to shoot any of those rockets as they start having a decent chance of hitting his own army.
I have only really seen the nomad hordes army and samurai armies used against chinese armies so this is all speculation. The nomad hordes did fairly well reducing the number of troops and then charging home. The rocket artillery was pretty effective once causing a big troop of horses to run away. But with them spreading out and moving up pretty quickly it was difficult for the rockets to hit.
The samurai did very well, they used mostly infantry and when the two sides met it was pretty much a slaughter. The rockets did some damage but weren't really able to slow the samurai down and even though they took off the odd rank it didn't matter that much as they managed to still win the combats pretty handily.
