I want to cancel my security question because i forgot the answer

What do you mean to cancel your security question? do you mean change the question answer or change from one question to another or stop using security question to authorization?

Anyway, if you still have your Apple ID password and can log on successfully, go to https://appleid.apple.com/ to modify your security questions.

If you forgot your password, I would suggest to go to Apple website (如果您忘记了自己的 Apple ID 密码 - Apple 支持) .

if nothing works, you may call Apple directly 400-666-8800 or visit Apple retail Store.