When using the triangular mesh method in path planning, aiming at the problem that the maximum threshold of the D-P algorithm for extracting waypoints is not easy to determine, this paper proposes a new method for extracting waypoints based on collision detection. The pure pursuit algorithm is used to track the way points and plan the motion of the differential driven robot. The experimental results show that the collision detection method is better than D-P algorithm in extracting waypoints. Finally, the motion planning experiment of differential driven robot shows that the motion trajectory planned by pure pursuit algorithm tracking waypoints is a smooth curve, which can effectively avoid obstacles on the map. The angular velocity and linear velocity of the robot are smooth functions with gentle changes. There are small fluctuations near the waypoints, and the fluctuation range is within the allowable value. The motion planning time is 0.049s, which can fully meet the actual needs. The results show that the motion planning of mobile robot based on road marking tracking is a simple and effective motion planning method.