Abstract: The paper adopts the Monte-Carlo method in the simulation and modeling of a rough sea surface, and uses the method of moment(MoM) to establish a model based on dual integral equations for transmission characteristics analysis of high-power microwave(HPM) at the sea surface. The model uses a smooth window function to modulate the incident uniform plane wave into a tapered one, which overcomes the edge effects caused by the sudden cutoff of the rough surface model. The model based on MoM is validated in comparison with Kirchhoff approximation, and it is used to analyze the impact of the rough sea surface geometry and sea water parameters on the HPM transmission coefficient. The results show that, the root-mean-square(RMS) height of rough sea surface affects the HPM transmission coefficient significantly, and larger RMS height leads to smaller transmission coefficient and more uniform energy distribution. The transmission coefficient increases as the real and imaginary parts of the sea water permittivity increase, and the impact of the real part is more evident.