It is difficult to choose or produce an appropriate radiation source for electromagnetic environment simulation of Microwave Landing System (MLS).We proposed to use a semiconductor laser with a big scale factor as the simulation model microwave radiation source.The physical similarities between the microwave and the radiation signal of semiconductor laser, such as the radiation intensity, spectrum characteristics, radiation field and polarization mode etc, were analyzed.A semiconductor laser was used for simulation of MLS radiation source scale model, and simulation of MLS operating process was realized.The result shows the feasibility of this method, which provides a new means for studying large electromagnetic system using small scale model simulation in laboratory.