In view of the problems of the traditional RRT algorithm in planning,such as too much randomness,too long search time and unable to achieve dynamic obstacle avoidance,the following three aspects were improved.Aiming at the too random search tree expansion direction of RRT algorithm,the search direction was expanded to the target point according to the obstacles proportion in the rectangle diagonal between the start point and the target point.It was compared with the traditional RRT algorithm in the environment with and without obstacles to verify the high efficiency of the improved algorithm.The key nodes were extracted from the path planned by the improved algorithm and optimized according to the key nodes.The improved dynamic window method was used to segment the optimized path.The fusion algorithm was compared with the improved traditional window method and RRT algorithm in terms of the number of inflection points and the length of the path.The experimental results shows that the fusion algorithm has high efficiency and the mobile robot can also well avoid with the temporary obstacles in the planned path.