Abstract: Located in the southeast part of the South Qilian orogenic belt in Qinghai Province, the Gangchadasi area has well-developed magmatic rocks, which intruded into Precambrian, Cambrian, and Silurian strata; nevertheless, their petrogenesis and petrogenic setting have not been reported by previous researchers. In this paper, in-situ zircon U -Pb geochronologic analysis of zircons was conducted in State Key Laboratory of Continental Dynamics by using LA-ICP-MS methods. The LA-ICP-MS zircon U-Pb dating shows that the ages of the granodiorite （10CL008）in Gangchadasi area can be divided into two phases: the concordia curve age of granodiorite 10CL008 sample is 254.8Ma±2.0Ma（N=13, MSWD=0.87）, belonging to Paleozoic Permian, whereas the other granite（10CL003）sample has an age of 236.3Ma±2.4Ma（N=13,MSWD=0.87）, belonging to Mesozoic Triassic. Geochemical characteristics show that granodiorite and granite belong to calc-alkaline and high K calc-alkaline metaluminous rocks respectively, with the original magmatic differentiation being transition from weak to strong. In REE and trace elements aspects, （La/Yb）N values are in the range of 2.23~10.38 and 4.52~14.98 respectively, with obvious LREE and HREE fractionation as well as positive anomaly of Ba and negative anomalies of Nb, P and Ti, suggesting the tectonic setting of island arc or active continental margin. Comprehensive studies show that granites had island arc or active continental margin properties, and were closely related to plate subduction in Paleozoic. In contrast, the Mesozoic granite inherited the characteristics from Paleozoic granodiorite, the magma components mainly came from the upper crust and formed in the early deep mantle, which was closely related to the remelting process of middle-lower crust caused by energy intrusion.