In the spaceborne/airborne forward-looking bistatic synthetic aperture radar (SA-FBSAR),due to the system platforms' remarkable velocity difference and the forward-looking mode,the range cell migration (RCM) not only depends on the target's twodimensional location,but also varies with the range location nonlinearly.And the nonlinearity is not just the slight deviation from the linear part,but exhibits evident nonlinear departure in the RCM trajectory.If the RCM is not properly corrected,nonlinear image distortions would occur.Based on the RCM model,a modified two-step RCM compensation (RCMC) method for SA-FBSAR is proposed.In this method,firstly the azimuth-dependent RCM is compensated by the scaling Fourier transform and the phase multiplication.And then the range-dependent RCM is removed through interpolation.The effectiveness of the proposed RCMC method is verified by the simulation results of both point scatterers and area targets. Due to the system platforms' remarkable velocity difference and the forward-looking mode, the range cell migration (RCM) not only depends on the target's twodimensional location, but also varies with the range location nonlinearly. And the nonlinearity is not just the slight deviation from the linear part, but exhibits evident nonlinear departure in the RCM trajectory. If the RCM is not properly corrected, nonlinear image distortions would occur.Based on the RCM model, a modified two-step RCM compensation (RCMC) method for SA-FBSAR is proposed.In this method, firstly the azimuth-dependent RCM is compensated by the scaling Fourier transform and the phase multiplication. And then the range-dependent RCM is removed through interpolation. The effectiveness of the proposed RCMC method is verified by the simulation results of both point scatterers and area targets.