Aiming at the problem of trajectory planning exploration when the starting point and ending point are known and the environmental information is unknown, an improved sparse A* UAV trajectory planning exploration method incorporating pheromone is proposed.Based on the local map information obtained by lidar and by introducing the pheromone, the cost function in the sparse A* algorithm is optimized to realize autonomous avoidance of obstacles in unknown environment without repeated exploration.On this basis, a physical implementation approach based on Robot Operating System (ROS) is proposed.Under spiral-form obstacle scene, it is verified that the method can avoid repeated exploration of the environment.In addition, the method is extended to the columnar obstacle scene.The experimental results show that the method can effectively achieve the exploration of trajectory planning in the unknown environment.