In recent years, with the acceleration of urbanization process, people become more concerned about security in public places like banks, official buidings and schools etc. Therefore, intelligent monitoring has become a hot topic in current research. This paper mainly studies the face abnormal occlusion events based on the indoor patrol car. Firstly, we extract the foreground of surveillance video. Then, we locate shoulders and use an ellipse to fit the area of head based on the foreground. And then, we determine the face area through the skin color rate. Lastly, we detect the eyes and mouth of the area through Haar detector to determine whether there are abnormal occlusion events. The experimental results show that the algorithm proposed can detect abnormal occlusion events effectively.