My car Radio is locked after changing my battery anyone know the unlock code?

No - that is the point, to avoid the radio being valuable to thieves. You don't mention make, model, or year, so I don't know if any of the shortcuts (like the Honda website available to American owners). apply. The certain way to get it, if you can't find it on a sticker in the glovebox or on the owner's manual, is to go to the dealer. You will have to prove ownership and maybe pay a fee. I like to email things like unlock codes to myself so I can get to it later but thieves can't.