Abstract: The Qiucheng Mo deposit is located in the Dehua-Yongxi-Yongtai ore-concentrated area of Fujian Province. It is the only one large-scale molybdenum deposit there. Ore bodies are mainly distributed in the outer contact of granite porphyry, fissure filling of the middle-late Proterozoic metamorphic rocks and the late Jurassic granites. The molybdenite is disseminated, veins and lump. Re-Os dating of six molybdenite samples collected from the main ore body in the deposit yields the model age from 150.1 Ma to 152.8 Ma, the isochron age of(150.8±1.6)Ma, and the weighted average age of(151.8±0.9)Ma. It can thus be considered that the deposit was formed in the late stage of Late Jurassic and related to the large-scale volcanic and intrusive rock activities. According to the rhenium content(14.31×10^-6-45.8×10^-6(one is 174.7×10^-6))and the ratio of Re and Os(much greater than 4)of molybdenum samples, it is inferred that the ore-forming materials of the deposit were mainly derived from the crust and possible addition of small amount of mantle materials. The Qiucheng Mo deposit may be the product of conversion process from the end of collision to the beginning of extension of the Paleo-Pacific plate towards the continental margin of East Asia.