Abstract: Synthetic aperture radar(SAR) which is a high resolution coherent radar is a significant space remote sensing method,and the resolution of SAR image determines its further application.Regularization method is effective to improve the resolution of SAR image,but the traditional iterative method for resolving the regularization model runs slow.The iterative formulation of image supper-resolution regularization model based on l_k norm was analysed,The analytic expression of the limit of iterative sequence which is produced by the iterative formulation was obtained.According to the conclusion,a new approach to solve the regularization model was obtained,and it could significantly simplify calculation.Simulation and results of MSTAR image processing show that the efficiency of the calculation improves more than 2000 times and the relative error between the presented method and the conventional method is only 6×10-9.