Synthetic Aperture Radar （SAR） radiometric calibration is the basis of SAR quantitative applications， and the calculation of the integral response energy of point targets is an important part of SAR radiometric calibration. In order to optimize the radiometric calibration method of high-resolution SAR system， according to the energy calculation model of integral method and the introduction of image context information， this paper proposes a calculation method of point target response energy of high-resolution SAR image based on the sliding window， which is verified by the airborne SAR data obtained by Xinzhou 60 remote sensing aircraft. The results show that the method can reduce the interference of background clutter， speckle noise and ground point target pointing error in SAR images on point target position selection， improve point target position selection accuracy， and the integral response energy obtained based on images is closer to the theoretical value of point target. Therefore， the method can enable the high-resolution SAR system to achieve higher radiometric calibration calculation accuracy.