Based on the teleseismic three component waveform data recorded by 31 broadband seismic stations in southwestern Yunnan,the radial P-wave receiver function is extracted,and the “crustal shear wave velocity model of China Seismic Science Experimental Field” is taken as the initial model to carry out refined structural inversion(vertical accuracy up to 2km),and Bootstrap resampling technology is used for statistics and evaluation,so as to obtain the S-wave velocity structure under each station,combined with the crustal thickness and Poisson's ratio distribution,The deep crustal structure and the seismogenic environment of strong earthquakes in southwest Yunnan are studied. The results show that:① The crustal S wave velocity distribution in the study area has obvious non-uniformity in both horizontal and vertical directions. There is an obvious and continuous low velocity layer within the depth range of 0～20km in the middle and upper crust,with an average thickness of about 15km and a maximum thickness of 20km. There is an obvious low velocity layer(about 8km thick)in local areas within the depth range of 20～28km in the middle and lower crust,which is mainly distributed in the area from the north section of Puwen Fault to the middle section of Amo River fault(around 23° N). In addition,such velocity layer is also found in local areas near the Honghe fault and north of Lancang River fault. ② From the perspective of seismogenic environment,Jinggu M_S6.6 and M_S5.8,Mojiang M_S5.9 earthquakes occurred in the low velocity layer of the middle and upper crust,and Laos M_S6.0 earthquake occurred in the transition region of high and low velocities. The Neogenic Fault zones are relatively developed in southwest Yunnan,and the reduction of seismic wave velocity may be related to the presence of fluids in crustal fractures or microcracks. The existence of NW trending Neogenic fault zones and the long-term effect of fluids in the study area prepare conditions for the sudden release of high strain in the zone. In addition,the four earthquakes all occurred in the high gradient zone of Poisson's ratio change,and the crustal thickness at the location where the earthquake occurred changed greatly. In areas with drastic changes in crustal thickness and Poisson's ratio,the composition of crustal materials is significantly different,and the crustal strain is easy to accumulate,which is conducive to the induction of strong earthquakes.