In order to evaluate the detection distance of laser detecting system, a simple method for estimating the detection distance of laser detecting system is presented based on the simulation of atmospheric transmission. The specific property of atmospheric transmission and the method for simulating the process were both analyzed in detail. Pointing to the imitation of laser detecting system, a test was carried out both inside and outdoor. Some valuable data was acquired. In the light of fluctuation of outdoor test data, influence factors were also theoretically analyzed. The testing result confirms that the method is feasible and practical to evaluate the detection distance of laser detecting system simply, to provide the distance reference for the outdoor test, and to heighten the test efficiency, which will be useful for the test of laser detecting system.