An improved A* and path smoothing algorithm was proposed to overcome the defects of A*-based paths for un-manned boats in inland lake environments including collision avoidance insufficiency,maneuver redundancy,and steering non-smoothness. Firstly,the evaluation function was enhanced by incorporating obstacle avoidance and steering costs. Sec-ondly,the redundant path of the A* algorithm was removed by iteratively generating the segmentations in a reversal man-ner. Finally,the steering trajectory was further optimized by addressing steering performance of the unmanned boat. Simu-lation experiments on a real inland lake map show that the im-proved algorithm significantly reduces the collision probabili-ty,steering angle and traveling distance,simultaneously,and thereby improving the steering performance of the unmanned boat.