I want to creat an apple ID，but it says my payment method has been declined. I've contacted the bank, my card has no problem...what can I do now?

What sort of card are you trying to use, debit or credit ? If it's a debit card then I don't think that they are still accepted as a valid payment method - they are not listed on this page and there have been a number of posts recently about them being declined

If it's a credit card then is it registered to exactly the same name and address (including format and spacing etc) that you have on your iTunes account, it was issued by a bank in your country and you are currently in that country ? If it is and your bank have confirmed that it's not being declined at their end then try contacting iTunes support and see if they know why it's being declined : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Account Management