Abstract: The seed plants' species variety and topographic unit diversity in Sichuan Province was analyzed quantitatively and their regional relationship was studied based on SRTM DEM data and plant distribution data by utilizing the powerful multi-source data processing and spatial analysis of ArcGIS10.1 software. The results showed that the topographic unit diversity index in Sichuan Province is between 0 and 0.86; the areas with lower value are located in Chengdu plain, Norgay wetland and alpine headwater area in northwestern Sichuan; the areas with higher value are located in the mountains around Sichuan Basin and the longitudinal Rang Gorge Region in western Sichuan. The variety of seed plants in Sichuan Province presents the same spatial distribution pattern and trend whether in the variety of family level, genus level, species level or in differentiation intensity in family level and genus level, increasing from the Sichuan basin to the mountains around the basin, and then decreasing again in alpines( western Sichuan alpine and western Pazhihua alpine). In overall, the seed plants' variety increases with the increase of topographic unit diversity index. The results reveal the regional scale topographic background of distribution of various seed plants, which provides a scientific theory and data support for ecological function regionalization and sustainable development of the river basin.