The invention provides a radar target back scattering simulation method influenced by Faraday rotation changes. The method comprises the steps of obtaining four complete polarization SAR compound images of an identical scene after various error influences are calibrated; obtaining a polarization scattering matrix S of a target; calculating a Faraday rotating angle omega caused by an ionized layer TEC value of each impulse transmission moment; calculating a polarization scattering matrix O influenced by the Faraday rotation changes; obtaining a back scattering coefficient influenced by the Faraday rotation changes; putting the back scattering coefficient influenced by the Faraday rotation changes into an SAR echo expression to carry out imaging processing and corresponding analysis. Through the adoption of the method, any influence on the back scattering coefficient and SAR imaging by the Faraday rotation changes can be simulated. In addition, radar target back scattering coefficients influenced by the Faraday rotation changes can be simulated easily and effectively based on existing SAR images.