Abstract: This paper recommends a new simplified sinc interpolation algorithm based on Range-Dopplor algorithm of SAR. By using the new interpolation algorithm, computation amount can be reduced, and the quality of SAR image can still be guaranteed. Two methods are suggested to realize the polynomial fit. One is Taylor expansion and the other is based on least square criterion to get the parameter of fitting polynomial. Error analysis is given to demonstrate the performance of these two methods. Finally, the algorithms are verified by using raw data of RADARSAT. The result shows that the proposed algorithms can reduce the computational complexity efficiently and the algorithms can be used in real time SAR signal processing.