Someone asked this the other day, and there was only my feeble reply ... which is:

Chinese fonts are multi-byte, which essentially means they use two characters storage for each character displayed. (this also means the font files can be several megabytes big!)

To use them in flash you are going to need a way to enter them and some fonts you can get both from the MS site in international font support. However I believe you may need a special version of Flash as well .... I'm not sure about that though.

When I had to do some japanese recently I resorted to doing it as vector graphics, in the end it seemed a lot easier.