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). If you change the user password in Users & Groups preferences, the keychain password is automatically changed to match it. If your user password is changed by an administrator, your keychain password may not be changed automatically, and you’re asked to enter the keychain password the next time you log in. You can update the keychain password to match your new user password. To unlock your keychain and change the password, you must know the current keychain password (which is usually the same as the previous user password).
Change your keychain password to match your user password
In the Keychain Access app on your Mac, click “login” in the Keychains list.
Choose Edit > Change Password for Keychain “login.”
If the keychain is locked, enter the previous user password for the computer, then click OK.
If you entered the correct password, a new window appears.
Enter the previous user password again in the Current Password field.
Enter your new user password in the New Password field.
Reenter the new user password in the Verify field, then click OK.
If you don’t remember your previous user password
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.
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 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.