This paper proposed a novel biometric system for user authentication, where the user ID is the person’s face and the password is his facial expression. The traditional authentication systems in the internet, mainly e-mail account access, online transactions, are based on alphanumeric user ID and password. However, these online systems are never guaranteed that the person is actual or another person who knows the user ID and password of that person. Therefore, there is always a chance of breaching the user’s authenticity and integrity. User ID and password of the traditional system can be broken or can be stolen to hack another person’s online activities. Only biometric authentication can guarantee that it is the genuine person. This paper proposed a face and facial expression based guaranteed authentication system for online activities. User can change his/her facial expression to change the password like the traditional systems. We tested our proposed method in many samples and it works properly.