I written by Mapper3's ROM.
But I can't chr-rom switching another bank.
How do i switch chr-rom another bank?

# sorry,i can't english speach & write & read well...

You need to have the right bank value stored in the ROM at the address you are writing to.
If we say you want CHR bank 2 and you write number 2 to $C000, then the number 2 must be in the ROM at address $C000. Its called bus conflicts, look at the solar wars source and you will understand.

Try something like this:
(Could go anywhere in ROM, I think. Just using $C000 for an example.)

.org $C000
.byte $00,$01,$02,$03

LDA #1 ; bank # to switch to
TAX
STA $C000,X

Sorry,But i can't understand...
Maybe i write Base Bootup address+bank if i wanna change to bank.
But it dose not change..

i write code this.

.inesprg 1 ; 16k prg bank
.ineschr 1 ; 8k chr bank
.inesmir 0 ; Horizontal
.inesmap 3 ; Mapper 3

.bank 0
.org $8000 ; Base Bootup

... this any code

.BankChange

sta $8003

... and more code

.bank 1
.org $E000
.org $FFFA
.dw NMI
.dw RESET
.dw IRQ

; NormalColor
.bank 2
.incbin "moji.chr"

; PincColor
.bank 3
.incbin "moji2.chr"

You must set .ineschr to 2 if you're using two CHR banks.

The iNES header needs to be set to the amount of banks in the ROM. Use ".ineschr 2" so the emulator will know there's 2 CHR banks available.

Thanx!!!
I change to bank!