Numerical simulation has advantages over theoretical and experimental research of controllable parameters and realizing ensemble average. Therefore, numerical simulation can be used to study the influence of atmospheric turbulence in big elevation link and other fields which can′t be built in experimental system. Using Zernike polynomial method and multi-layer phase screen theory, the atmospheric multi-layer phase screen model is established. The numerical simulations of Gaussian beam propagating in horizontal link (0°) and big elevation link (30°,60°) are achieved. Using the empirical formula for the variance of angle of arrival (AOA) fluctuations in horizontal link, the results of three groups of 900 times numerical simulation in horizontal link are analyzed. The results show that the error of variances of AOA fluctuations between simulation and experimental values is within 5%, and this model is effective. This work is important for studying the influence of atmospheric turbulence in free-space optical communication system.