YEEEEEEEEEEEESSSSSSSS! I found out a way to play GBA game on DSi, ha ha.
Today, I search how to play GBA on DSi, and I found out a website http://www.gbadsi.com/, it show that the DSi playing a GBA game, it's amazing.
As I know that the VGBA *.sav file is compatible with SC *.sav file, you can copy SC *.sav file to you computer and rename *.sav file the same as *.gba file, such as mario.gba should have a mario.sav together. Then VGBA can recognize it.