Aiming at the problem of area coverage reconnaissance path planning for fixed-wing UAVs,a concave area coverage path planning method based on improved Ant Colony Optimization(ACO) is proposed.The vertical load reconnaissance model is established,and parallel coverage strategy is introduced,the flight direction is determined by rotating calipers algorithm.For the irregular concave polygon region,a multi-strategy concave polygon conversion method combining concave point removal and region decomposition is proposed.The coverage path planning problem is transformed into an optimization problem of searching the optimal strip traversal order,and Dubins turning paths are established.The problem is solved by improving the heuristic function in ACO,introducing adaptive pheromone volatilization coefficient and 3-opt algorithm.The experimental results show that the proposed method can effectively realize the concave area conversion and obtain a shorter area coverage reconnaissance path,which can provide theoretical support for the research of autonomous regional reconnaissance of unmanned reconnaissance aircraft.