A 3-D shear wave velocity model of Southeastern Margin of Tibetan Plateau crust was constructed by Markov Chain Monte Carlo inversion, based on Rayleigh wave phase velocity tomography results which are obtained from ambient noise interferometry and tele-seismic two plane wave analysis, using seismic data of 137 permanent stations from China digital seismic network and 332 portable stations from ChinArray. The velocity model indicates the presence of an interconnected lower crustal channel flow in southeastern margin of Tibetan plateau, which is represented by an interconnected low shear wave velocity zone with Vs < 3.55 km/s. It consists of three parts which respectively locates beneath the Panzhihua area and to its west and east. The lower crustal channel flow from Tibetan Plateau is blocked by rigid lower crust of the Sichuan block and turns to flow through Emeishan area to the south direction, which alters the lower crust of Emeishan large igneous province (ELIP) together with the lower crustal channel flow beneath Pahzhihua area, thickening the crust in this area. It is infered that the lower crustal channel flow beneath the southeast margin of Tibetan Plateau ends at about 24°N, and has the potential to extend further south, which has the role to extend the scope of crustal thickening in the future.