In complex environments with narrow roads and many obstacles, Rapidly-exploring Random Tree* (RRT*) algorithm has the problems of high sampling randomness, low efficiency, slow convergence speed and tortuous path.In combination with an improved collision check mechanism RRT* algorithm, an improved Bidirectional RRT* (Bi-RRT*) algorithm is proposed.The algorithm first performs node sampling in the dynamic target area to reduce execution time.Then, the target bias strategy is introduced to the node expansion stage to reduce the randomness of tree growth, and the bidirectional tree growth mechanism is adopted to improve the convergence speed.Finally, redundant nodes on the initial planning path are eliminated to increase the smoothness of the path and reduce the memory requirement of this algorithm.Experiments are conducted in simulation environment.The results show that the improved Bi-RRT* algorithm reduces the randomness of execution and the number of iterations, and the convergence to a smooth path is realized in a shorter time.