In the shooting scenes of intelligent transportation system, the phenomenon of vehicles occlusion is caused by the distance between vehicles and the angle of camera shooting, which increases the difficulty of target vehicles detection and tracking. A concave region detection and segmentation algorithm based on contour feature points and contour concavity and convexity is proposed. Firstly, we use background difference method to extract the vehicles region. Meanwhile, according to the length-width ratio and the duty ratio of the outer rectangle of the vehicles area, the multi vehicles occlusion in the area is judged, and through convex analysis algorithm to extract concave area. Then, the edge feature points of concave area are determined by Freeman chain codes, and the feature points are concave analyzed. Finally, the Bresenham segmentation method is used to segment the occluded vehicles by matching the segmentation points. The experimental results show that the algorithm can effectively solve the problem of occluded vehicles segmentation, and has better scene adaptability compared with other algorithms.