Abstract:Using finite element method on the southeast margin of the Tibetan plateau, this paper establishes a more detailed and accurate three dimensional finite element model of elastic, selects the stress of the nine different boundary conditions, applies optimization analysis for each project in post-processing, analyzes the corresponding station deformation GPS simulated values and measured error, and finally chooses the best solution as palaeotectonic stress field. Results show that around four million years ago the ancient stress field of the southeast margin of Tibetan plateau mainly originated from intense collision of the Indian plate NNE with the Chinese mainland plate. The mainland of China, especially the Tibetan plateau in southwest region, is the main power source of the tectonic stress field, and controls how the various blocks interact and their motion patterns. The paleostress field on the southeastern edge of the Tibet plateau mainly includes the following sources: The NE-WS directional stress in the southwest is about 70 MPa directly from the Indian plate. Southern NS force 33 MPa; lateral NW-SE blocking force of southeast Yangtze block is 56 MPa. At the same time, the strong EW blocking force of the Yangtze block in the eastern north is 90 MPa, and these forces act together on the southeastern edge of the Tibetan plateau, forming a complex stress field.