Based on observation data from the China Earthquake Networks Center, the Focal Mechanism (FOCMEC) approach estimated the primary mechanism solutions of 606 minor and medium-sized earthquakes in Sichuan and Yunnan from 2014 to 2023. This method is based on P wave initial motion polarity and amplitude ratio. The tectonic stress field in the area was inverted using the Bayesian right-handed triangular pyramid technique (BRTM). The study discovered that a number of variables, including plate movement, variations in crustal structure, and crust-upper mantle connection, regulate the stress field in Sichuan and Yunnan. The Qinghai-Tibet Plateau’s southeast border is compressing, primarily affecting the northern regions of Sichuan and Yunnan. This stress field is clearly zoned. The Qinghai-Tibet Plateau squeezes the northern portion, and the P axis runs northeast-southwest. A progressive north-south bend on the central P axis indicates east-west tension. Strike-slip features predominate in the southwest. The spatial distribution of Bishop ratio reflects the differences in regional stress environment. The plate movement primarily drives the geographical tectonic stress field, and the fault zone is essential to the regional stress release mechanism, as evidenced by the consistency of the maximum major stress direction and GNSS velocity field data. This study reveals the spatial distribution physiognomies and dynamic mechanism of the tectonic tension field in the Sichuan-Yunnan region, providing an important scientific basis for a deeper understanding of the seismic activity, tectonic deformation mechanism and earthquake hazard assessment in the region.