The wavelet multi-scale decomposition method was used on the DEM data to generate a landform data with low frequency topographic signal which can indicate the tectonic zone information. According to the result, the third order approximation map of DEM can indicate the large scale tectonic characteristics which represented by the low frequency signals in landform. Based on the third order approximation map, we calculate the slope to identify, reclassify and extract the tectonic blocks and its margin tectonic belt around the Qinghai-Tibet Plateau. Compared with the traditional tectonic divisions, the automatic zonation based on DEM can characterize most of the important tectonic blocks and its margin belt, and it is found that the scale of the boundary between the Lhasa Block and the Qiangtang Block is larger than the boundary between the Qiangtang Block and the Bayan Har Block.