Abstract: An improved numerical simulation method of Doppler Spectrum of sea echo for ground-based microwave wave radar is presented based on a study of scattering mechanism of microwave with ocean surface and some research results by W.J.Plant et al.According to the theories of Bragg scattering,composite surface,linear wave,and the expressions for NRCS of different polarization types,the characteristics of Doppler spectrum is displayed in shape,amplitude and time domain,and Doppler spectra of different ocean conditions are compared and qualitatively analyzed.Accordingly,it can be concluded that the simulation results reflect actual ocean environment and accord with objective law,which provides significant theoretical model for oceanographic observation by microwave wave radar and information extraction of sea state,especially parameters of wind,wave and current.