To solve the problem of slope reduction caused by the lack of high-resolution Digital Elevation Model ( DEM ) on the surface of moon, Mars and other planets, we propose a low-resolution slope compensation method involving slope change rate factors. It is an improvement on the existing linear compensation method by incorporating slope change rate into the compensation model to obtain better accuracy for slope compensation. In this paper, lunar and Martian data are used to verify the method. Several lunar and Martian low-resolution DEMs covering a variety of terrains are selected and compensated using the improved method. Then they are validated using slopes generated from the high-resolution DEMs. The results show that after applying the proposed compensation function, the compensated slopes can represent the terrain features of the lunar and Martian surface better compared to the original low-resolution slopes. Meanwhile, the proposed method considering the slope change rate is more effective than the traditional linear compensation method. Based on the improved method, the overall and hierarchical compensation models suitable for various lunar landforms are established and the low-resolution Martian slope data covering 50 km×50 km of the Tianwen-1 landing site are compensated and analyzed.