Indoor mobile robot navigation based on the vision system is a hot research field in recent years. Structured light method is a kind of three dimensional measuring technology which is widely used in mobile robot vision system. In this paper, mobile robot obstacle detection system in indoor environment is designed, linear structured light which is projected in front of the robot assists camera to gather environment information. With the image processing algorithm, we can detect the change of linear structured light per frame, compare with the standard image to reach a conclusion that whether there is an obstacle and then calculate the characteristic value of the obstacle.