Abstract:In view of the problems in parking lots of low parking efficiency and parking set utilization rate. combining the parking model of underground parking lot,translating the question of parking efficiency into the question of dynamic parking probability, evaluate the algorithm with parking probability and algorithm efficiency, an improved A* algorithm with constrains is proposed in this paper. The experimental result based on structure of parking lot and VC++6.0 platform show that both the parking probability and algorithmic search efficiency are increased. in some way, the application of improved A* algorithm in parking lots increase the user parking efficiency and parking set utilization rate,reducing the time that parking users will spend blindly looking for parking Spaces, so it has definite pragmatic research value in parking lots.