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Under the shadow of the far-field effect of the India-Eurasia collision, the Tianshan orogenic belt underwent tectonic re-activation in the Cenozoic, accompanied by strong tectonic deformation and frequent large earthquakes. Bounded by two rigid cratonic blocks located in its north and south, a series of marginal foreland fold-and-thrust belts are developed within the Tianshan orogenic belt and continue to develop to the bilateral pull-apart basins. Meanwhile, the faults in the orogenic belt are reactivated. The deformation caused by thrust-related structure accounts for larger than 50% of the total convergence of the Tianshan Mountains, which results in the most active structure with large earthquakes in the Tianshan area. Therefore, it is of great significance to study the dynamic process of the newly generated and reactivated thrust-nappe structures in Tianshan orogen via numerical modeling. This paper selects a classical cross-section profile in the western segment of the Southwest Tianshan Mountains, which contains the Kalpin-Maidan-Nalati-Kemin fault system from the south to the north. We attempt to establish a two-dimensional plane strain, viscoelastic finite element model, by treating the regional faults as a whole fault system and considering the topography, fault geometry, and GPS data. The displacement and stress fields of the model are retrieved, the short-term cumulative deformation field of the overall fault system is analyzed, and the rate of Coulomb failure stress change of each fault is also considered. The results show that the deformation is concentrated in the middle and southern parts of the Southwest Tianshan Mountains. In contrast, the deformation of the Kemin fault in the north is relatively small. According to the Coulomb failure stress changes of these four faults and the historical earthquake catalog, the potential seismicity of each fault is qualitatively analyzed. Our preliminary results suggest that the possibility of large earthquake occurrence is higher in the Kalpin fault, Maidan fault, and Nalati fault but lower in the Kemin fault in the near future. [ABSTRACT FROM AUTHOR]