CO_2 and CH_4 play a significant role in the global climate change and carbon circulation and can be used to monitor their origin and tectonic activity.In this paper,we carried out investigations on the gas compositions,carbon isotope ratios of CO_2 and CH_4,and He isotope compositions from the Qiangtang Basin and its adjacent areas.Our results show gas samples from Beiluhe,Bucha Lake,and eastern Tuotuo River are N_2-rich with N_2 over 75%.The contents of CO_2 and CH_4 are only 3.45%-20.91% and 0-3.58%,respectively.CO_2/~3He and CH_4/~3He and carbon isotopic values of CO_2 and CH_4 suggest that both CO_2 and CH_4 from Bucha Lake are biotic without mantle-derived CO_2 and He,whereas those of Beiluhe and eastern Tuotuo River are abiotic.Southern Erdaogou Depot,branch of Tuotuo River,and Tanggula Mountain Depot are enriched in CO_2 with more than 96%.The CO_2 was at least partially originated from mantle,trace amount of CH_4 was abiotic and derived from mantle-derived CO_2;He was primarily originated from crust with only 2.15%-5.66% of mantle-derived origin.These results show that the emitting of large quantity of mantle-derived CO_2 is likely to be ascribed to the presence of Bangong Lake-Nujiang River,Hoh Xil-Jinsha River sutures and the Cenozoic volcanism in northern Tibet.Nevertheless,the estimated small fraction of mantle-derived He may result from the low opening degree at the bottom of fault zones and possibly reflect a geological setting of strong extrusion and an increase in crustal thickness.