The first step, When you log into the account successfully, click on the user center in the upper right corner.
Then click the transaction password in the security function bar on the left side of the page, it will be redirected to the modify transaction password page, click the forgot password.
Fill in the required information and submit.then it will show the modification is successful.
(you will be prompted to keep your assets safe. If the trading password is modified, you will not be allowed to withdraw coins within 24H or sell assets in legal currency transactions.)