Hi Chia Ming Liu,
Thank you for writing. We haven't seen any problems with the Chinese fonts until now. Actually RadContols for Winforms render fonts using the standard windows API.Please, could you provide some screenshots and information about the machine regional settings? I would like to suggest to try the following:
1) Try to change Ribbon Font to another one?
2) Set UseCompatibleTextRendering property of RadRibbonBar to false.
I look forward to your response.
the Telerik team