Abstract: In order to simulate the real sea surface echo signals of GNSS, sea clutter signal is essential besides GNSS reflection signal from the sea surface. Modeling and simulation of sea clutter is the decisive factor of the fidelity of echo signal simulation. In this paper, the grid mapping method is used to divide the sea clutter elements, and the appropriate amplitude distribution model and power spectrum model are established to complete the modeling of airborne sea clutter signal.Finally, the simulation of sea echo signal is carried out and compared with the measured data. The result indicates that the correlation coefficient between the simulation data and the measured data is better than 0.9, which proves the validity and rationality of the method.