In this paper, a EM simulation modeling method for the two dimensional time varying sea surface microwave propagation is proposed. It is not only the electromagnetic simulation model, but also is a statistical analysis model of rough sea surface channel. Firstly, PM spectrum, Fourier transformation and Creamer transformation are adoped together to build typical linear and nonlinear sea surface models. Second, electromagnetic sacatering characteristics of sea surface under typical sea conditions based on the geometrical theory of diffraction is computed based on models proposed. Third, the method of estimation method of effective scattering area is analyzed to meet the requirements of electromagnetic simulation. Last, to improve the computing power, a method of extending the simulation area of rough sea surface is presented, and the effectiveness of the extension method is demonstrated and the optimum sample size of electromagnetic calculation of rough sea surface is documented in detail.