There are lots of intrusive rocks composed of amphibole pyroxenite, gabbro, norite, pyroxenite and augite peridotite in Riyueshan-Hualong basic-ultrabasic rock belt of South Qilian Mountains, which are related to copper-nickel mineralization. The data suggest that the ore-forming materials were derived from both the mantle and the crust. The content of crust-derived Os is estimated to be 20%~28%. The crustal contamination might have been one of the most important factors for copper and nickel accumulation in the Yulonggou intrusion.