Abstract: Timing of the South Tianshan suture zone between the Central Tianshan-Kazakhstan-Yili terrane and the Tarim craton is very important for the final closure of the South Tianshan Ocean, the southwestern part of the paleo-Asain Ocean. Zircon LA-ICP-MS U-Pb dating of the granitic plutons in Kokshal area of the South Tianshan Mountains indicates that these plutons were emplaced during the Early Permian (273~283Ma). Spatially, these Early Permian plutons occur simultaneously in the Kazakhstan-Yili terrane in the north and the Tarim craton in the south, with one of the plutons directly crosscuting the Baleigong ophiolite, implying that the South Tianshan suture zone was formed before the emplacement of the Early Permian plutons. The results obtained by the authors further prove that the South Tianshan Ocean was closed at ~300Ma.