Abstract: In the second phase of Chinas lunar exploration program, an actual landing on the lunar surface will be included, and so greater flexibility with regard to landing locations is one of the many improvements planned. An optimized algorithm based on the Monte Carlo method was proposed to calculate the probability of safe landing under various specified conditions on a large number of different terrains generated in simulation experiments. Topography simulation was based on the actual characteristics of the lunar surface topography and statistical distribution of lunar craters and rocks. The algorithm depended on the lander attitude information and landing plane envelope model. Engine control, attitude control and dynamic property were not considered in simulation experiments. Only under same lander profiles in one group tests, the experimental results were reasonable. The landing territory , lander profile and safety parameters were simulated on computer by this method. It could be applied to bothground simulation experiments and real-ime analyzing possibility of landing safety during soft landing on the lunar surface. These improvements in the descent and landing are essential to the development of a lunar outpost, and also for increasing the number of potentially accessible lunar sortie locations.