The Keping-tage fold-thrust belt in southwest Tian Shan is seismically active, yet most well-recorded earthquakes occurred south of the mountain front, hindering our understanding of the orogenic process to the north. The 2020 Mw6.0 Jiashi earthquake is an important event with surface deformation in the nappe structure well illuminated by InSAR. Here, we employ the surface deformation and relocated aftershocks to investigate the fault slip distribution associated to this event. Further added by an analysis of Coulomb stress changes, we derive a fault model involving slips on a shallow low-angle (~10º) north-dipping thrust fault as well as on a left-lateral tear fault and a high-angle south-dipping reverse fault in mid crust. Our results reflect the basement-involved shorterning activated by a thin-skinned thrust faulting event with the surface deformation implying the basin-ward orogenic process of the southwest Tian Shan.