Abstract: Although numerous previous studies, no direct evidences of geological ages are recorded for the Lancang Group Complex in western Yunnan. The U-Pb age data of the detrital zircons in sericite quartz schist from the Lancang Group Complex in the Changputang-Datianshan zone have provided convincing evidence for the formation age of the Lancang Group Complex. The cathodoluminescence (CL) images show that these zircon crystals generally display the well-defined oscillatory zonation and suggest a magmatic origin of the zircons. The age data for the detrital zircons in the sericite quartz schist sample PM08-B1 range between 452 and 3016 Ma, with the youngest age group of 452 ±26 Ma, implying that the maximum depositional age of the Lancang Group Complex is less than 452 ±26 Ma. One zircon grain with a U-Pb age of 255 ±3Ma exhibits a slight cathodoluminescence image and has no internal structures, which is characteristic of a type of metamorphic recrystallization zircons and in general aggrement with the previous data. In general, the Lancang Group Complex is dated at a depositional age of less than 452 ±26 Ma, The U-Pb age (255 ±3 Ma) of the metamorphic crystalline zircons reveals that the metamorphic events once took place during the Late Permian.