This paper introduce a new method for extracting internal wave parameters from SAR image. The surface current induced by the internal wave is simulated according to the KDV equation. Then the radar cross section induced by the internal wave can be calculated. The wind speed and pycnocline depth are modified using the dichotomy method step by step which causes the simulation radar cross sections close to those measured from the SAR image. Finally, both the wind speed and pycnocline depth can be obtained. This method is tested on the example of an SAR image. The simulated internal wave signal is consistent with the radar cross sections of SAR images. Their correlation coefficient is up to 90%, which indicates that this method is convergent and applicable.