Abstract: Based on the Geophysical Mode Function SASSⅡ and CMOD,we simulate the sea backscattering coefficient of electromagnetic waves which vary with the Scattering Azimuth in the condition of different incidence angle and wind speed. Ac -cording to the analysis of the figure about the sea backscattering coefficient differential between the condition of headwind and downwind of the two Mode Function,we propose a new way that eliminate the 180°fuzzy of wind inversion by use of the sea backscattering coefficient differential between the condition of headwind and downwind.