Aiming at the problems of low search efficiency,long path and too many turning points in the three-dimensional path planning process of bidirectional RRT algorithm,an improved bidirectional RRT algorithm is proposed on the basis of bidirectional RRT algorithm.The improved bidirectional RRT algorithm is extended from the starting point and the end point at the same time,and a new target bias sampling strategy and dynamic step size strategy are introduced to make the random tree sampling have target directedness,which solves the problem that the original algorithm is too random.The node pruning strategy is used to optimize the generated path and delete the redundant nodes in the path.The B-spline curve is used to smooth the path after pruning optimization.The simulation results show that the improved algorithm can generate a smooth path that satisfies the UAV performance constraints in a three-dimensional environment,which can effectively shorten the path length and improve the path planning speed.