Abstract: Based on the equivalent-squint range model, an modified-k algorithm for wide-field and high-resolution spaceborne spotlight SAR is proposed. In order to process the wide field and high resolution spaceborne SAR data precisely, by taking use of the relationship between the range and the equivalent velocity, the Stolt mapping of the classical-k algorithm is modified. The modified Stolt mapping takes into account for the range-dependence of the equivalent velocity, so that the range cell migration is corrected accurately. Based on the modified Stolt mapping, the modified-k algorithm is presented, which guarantees the uniform image quality along range and is validated by the simulation.