If you need to update your keychain password on Mac
By default, your keychain password is the same as your user password (the password you use to log in to the computer). You can change the user password in Users & Groups preferences and the keychain password is automatically changed to match it.
If you don’t remember your previous user password, you need to reset your default keychain. Resetting the default keychain deletes all the passwords saved in the keychain, but should allow you to sync up your login password and the password stored in the keychain.
In the Keychain Access app on your Mac, choose Keychain Access > Preferences.
Click Reset My Default Keychain.
In the Finder on your Mac, choose Apple menu > Log Out. When you log in again, save your current login password in a keychain.
If your user password was reset because you forgot your password and you can’t provide the old password for the keychain, you won’t be able to access the information in the old keychain, and a new blank keychain is created.