Identification on the sedimentary age of metamorphic rocks of Gaoligong Group in Tengchong block, western Yunnan and its tectonic setting is a key to study the evolution of the Prototethy tectonic zone and the relationship between Tengchong block and Gondwana. Petrological and geochemical data show that the metamorphic rocks in Gaoligong Group are composed of meta- sedimentary and- igneous rocks. The meta- sedimentary rocks are mainly comprise of schist and Para gneisses with a little of marble and quartzite, which is metamorphosed from greywacke and mudstone with a little limestone and siliceous rocks deposited in abyssal- bathyal environment in active continental margin. Detrital zircon LA- ICP- MS U- Pb dating show that the zircons in the meta- sedimentary rocks derived mainly from the igneous rocks related to the amalgamation of Rodina and Gondwana supercontinents as well as the subduction of the Prototethys (900~1000Ma and 500~600Ma). Weighted mean age of the youngest detrital zircon groups in four samples ranged from 507 to 510Ma, and without any significant ages less than 470Ma, show the protolith of meta- sedimentary rocks in Gaoligong group was depositing from 510 to 470Ma. These sedimentary rocks were deposited with some igneous sediment on the hanging side between ocean trench and island arc during the subduction of prototethys oceanic crust toward the Gondwana continent in late Cambrian- early Ordovician.