The Yulekenhalasu medium-size porphyry copper-(molybdenum) deposit occurs in the diorite porphyry, with some mineralization also observed in the porphyroid biotite quartz monzonite and volcanic rocks of the Beitashan Formation. According to cutting relationships of the ore veins, mineral assemblages, paragenetic sequence and ore fabrics, the ore-forming process can be divided into three metallogenic periods: porphyry, shear deformation and supergene periods. The combined isotopic data imply that the ore-forming fluids of the sulfides-K-silicate stage in the Yulekenhalasu Cu-(Mo) deposit were mainly derived from magmatic fluids, with a minor part from the meteoric water, and the fluids of the carbonate stage were mainly derived from the meteoric water, with a minor part from magmatic fluids.