The Triassic granites are widespread in the western Kunlun Mountains. However, the timing and tectonic regime that accounted for the granites are poorly known due to limited data in geochronology, geochemistry and structural geology. In this paper, we report our structure observation and U-Pb zircon ages of the two types of Triassic granites, and use these data to place chronological constraints on the tectonic evolution of the western Kunlun orogenic belt. The gneissic garnet-bearing granite was crystallized at 241 Ma, whereas the horblende-bearing granite emplaced at 228 Ma. In terms of structural characteristics and geochemistry of the granites in conjunction with previous studies, we interpret that the garnet-bearing gneissic granite (S-type) was formed during the collision between the Tianshuihai terrane and the Southern Kunlun terrane following the closure of a branch of the paleo-Tethyan ocean along the Mazha-Kangxiwa suture zone, the block hornblende-bearing granite was formed during post-orogenic extension. On the other hand, the granites of ca. 220-190 Ma in the southern Kunlun Mountains were part of a new magmatic arc, which was formed after the collision of the two terranes.