Abstract: The middle-scale Xichao molybdenum ore deposit was a newly discovered porphyry deposit in eastern Fujian Province. The LA-ICP-MS zircons U-Pb dating of biotite adamellite and molybdenite Re-Os isochron dating yielded a U-Pb age of 115±1.2 Ma(MSWD=0.90)for biotite adamellite closely related to mineralizaiton, and a weighted average ¹⁸⁷Re-¹⁸⁷Os mode age of 112.6±0.7 Ma(MSWD=0.82)for molybdenite, with a ¹⁸⁷Re-¹⁸⁷Os isochron age of 113.4±0.9 Ma(MSWD=0.11). Basicaly same rock- and ore-forming ages, maybe with the former later than the latter, were products of late Early Cretaceous magma-mineralization. The characteristic of Re content in the molybdenum suggests that ore-forming material of Xichao molybdenite deposit originated from deep crust-mantle mixing. The Xichao molybdenum deposit probably formed in an extensional setting due to continuous subduction of Paleo-Pacific plate toward Eurasian continent, i.e. lithospheric thinning process, and may be the product of partial melting of lower crust material caused by uprising and heating of local asthenosphere.