Abstract: This study employed land transfer matrices, topographic analysis, and optimal parameter geographic detectors to investigate the evolution characteristics and driving mechanisms of territorial spaces in Xizang from 2000 to 2020. Key findings included: (1) The spatiotemporal evolution of territorial space in Xizang over the past 30 years was marked by the dramatic expansion of urban space from a ‘small scale’to a ‘large proportion,’ the contraction of agricultural space from a ‘small scale’ to a ‘small proportion,’ and significant dynamic transformations within ecological space. The pattern of urban space showed a notable trend of ‘large dispersion and small concentration,’ and the urban-agricultural contradiction in the Three-Rivers Region was highlighted. The spatial layout of livestock-farming-forest was undergoing profound restructuring; Simultaneously, the melting of glaciers led to the violent expansion of Xizang′s water-related ecological space. (2) The spatial distribution and cross-conversion of terrain gradients in Xizang were significantly different. Notably, urban and agricultural space tended to concentrate in lower valley regions, while ecological space tended to ascend in uphill. The third level served as a crucial topographic node influencing urban development and cultivated land protection. (3) Four types of factors, including physical geography, social economy, policy engineering, and transportation location, jointly restricted the spatial evolution of land in Xizang. There were obvious differences in the intensity of each type of factor and the number of significant factors in different transformation directions. Based on this research, it was recommended that the conflicts between urban and agricultural spatial resources be addressed, the enhancement of ecological services′ value be prioritized, and the sustained effectiveness of ecological restoration projects be ensured. Scientific guidance should be provided to align territorial space with topographic gradient layouts. Additionally, planning the overall regional layout of the ‘three regions and three lines’ would positively impact the optimization of territorial spatial patterns in Xizang.