Abstract: We present a new method for simplifying terrain using terrain significance information (TSI) index from DEMs. Firstly, TSI index of each grid cell based on DEMs is extracted. Secondly, critical elevation points are extracted from original DEMs for constructing target DEMs with proper TSI index threshold values. Finally, 1∶50 000 DEMs taking as reference target, and very important points (VIP) and three\|Douglas\|Peucker (3DD\|P) being as verify methods, the terrain simplification effect of the DEMs reconstructed with the method is analyzed and evaluated. The results show that the terrain simplification method based on TSI index is not only with better numerical precision, but also effective in reducing the terrain distortion by keeping terrain skeletons to meet the demands in different levels of multi\|scale terrain digital modeling.