Thanks for the reply. I'm a normal user of China, I think the "YellowBarDynamic - unicode" is the best theme for the chinese characters.
Everything is OK till I format my sansa clip+ by mistake, so I re-install the rockbox, failed to install that theme via Rockbox Utility, so I download it maually form website, then unzip to the root directory of player, but it doesn't work when I choose the theme in the Rockbox. Now I use "uming_chinese" instead of it, but the title and artist disapear once start playing songs, it maybe doesn't compatible with 3.11.2, because it is too old after all.
Thanks again for the good firmware, have to say that it's better than the original firmware.