i finally figured out what is the problem,
it is totally mysql problem, by default, mysql backup will export .sql in "ansi as utf8", thats mean mysql backup will export latin1 in default no matter you have already set your server to utf8. so, if you restore that "ansi as utf8" table into the database, and then you install new component to the table, all the newly install tables will become latin1 and collation latin_swedish_ci, no matter you change it to utf8, the chinese data inside will not properly display.
i fixed the problem as follow:
using mysql administrator to backup the database, and then use notepad++ to open it, you will see that the encoding is "ansi as utf8", change the format to "utf8 only" and then save, after so, restore it back by my sql administrator with default settings, then it should be no problem anymore, newly added component (tables) are utf8 now.