UAVs must be able to detect obstacles during flight and avoid the obstacles precisely.In order to make the UAV safer in flight, a method of obstacle avoidance is proposed combining binocular stereoscopic vision with optical flow.The binocular stereoscopic vision is used to obtain reliable parallax value through edge index algorithm, to get the spatial depth information according to the parallax convergence angle, thus to identify the object distance.The SIFT based optical flow method can obtain the movement speed of the obstacle relative to the camera at each moment.In order to obtain more accurate position information more quickly, the stereoscopic vision and optical flow are combined together.The experimental results show that this method can effectively improve the efficiency and precision of obstacle avoidance.