Self-service bank including ATM has become a part of people's daily life. However, the concomitant insecurity factors including PIN number stolen caused by shoulder surfing attack can lead to great lose. Considering that ATM is all equipped with cameras which can capture the real-time videos around, we propose an anti-shoulder attack system on ATM in this paper. Through the combination of human body and face detection, the potentially suspicious subject can be realized. Then, the ATM users will be reminded to pay attention to the surrounding, which can prevent the users from encountering shoulder-attack based peeping, sneak attack or other dangerous behaviors.