Abstract：The Sangshuyuanzi ductile shear zone in the central segment of the South Tianshan is an east-west-trending shear zone, in which foliations, lineations and asymmetric structures are well developed. Based on a kinematic analysis,the authors think that the Sangshuyuanzi ductile shear zone is of sinistral strike-slip nature. 40Ar/39Ar dating of muscovites from mylonite in the shear zone yields a plateau age of 393±6 Ma and an isochron age at 389±3 Ma. 40Ar/39Ar dating of biotites from en-echelon fractures in the zone gives a plateau age of 366.5±2 Ma and an isochron age of 365.0±3 Ma. According to the above-mentioned study, combined with the regional tectonic background, this paper suggests that the Sangshuyuanzi ductile shear zone is a syncollisional strike-slip tectonic zone formed by oblique collision between the Tarim plate and the Kazakhstan-Ili plate, which resulted in strain partitioning parallelly to the boundary of the two plates.