Vehicle detection is critical to traffic surveillance and management systems. In real outdoor daylight scenes, shadows cast by moving vehicles are often detected as a part of the moving vehicles since shadows move in accordance with the movement of vehicles, which will heavily affects accuracy of vehicle detection. In this paper, an algorithm is proposed to suppress the moving cast shadow for vehicle detection based on four properties of the moving cast shadow. Simulation results indicate that the proposed algorithm can effectively suppress moving cast shadows of input image, which helps to improve accuracy of vehicle detection.