I have read all the post in http://www.experts-exchange.com/Hardware/Q_20848064.html
And I have used the tool killdisk.exe to erase the FlashDisk,it could be erased but it couldn't be converted to FAT32,only to Fat & NTFS.
Follow the direction of LucF to use command prompt,and response me below.
G:\>format G: /FS:FAT32
Insert new disk for drive G:
and press ENTER when ready...
The type of the file system is FAT.
The new file system is FAT32.
Format cannot run because the volume is in use by another
process. Format may run if this volume is dismounted first.
ALL OPENED HANDLES TO THIS VOLUME WOULD THEN BE INVALID.
Would you like to force a dismount on this volume? (Y/N) Y
Volume dismounted. All opened handles to this volume are now invalid.
The volume is too small for FAT32.