Make sure that the font you are using in Access is in fact working properly in Excel. Each character in a font set is actually passed as a code number, the character "A" for example is decimal 65. All Alpha-Numeric font sets use 65 for the letter "A". It sounds like to me that for some reason, Excel is not using the Font set you think it is but some alternate instead.
some of the character(such as Ç ) cannot display in the Excel normally, what was going wrong??
Did you try to export it manually, I mean from the File menu/Save as .... and choose the Excel, I think it should function in this way, because I use the german version of Access97 and have your same problem, but when I export it manually, it functions.