The Larong W- Mo deposit, located in the southeastern part of the Leiwuqi- Zuogong metallogenic belt, is the first giant porphyry W- Mo deposit discovered in eastern Tibet. The metallogenic setting of this deposit is unclear due to lack of constraints on metallogenic chronology. Six samples of molybdenite from ore- bearing quartz veins were carried out for Re- Os isotopic dating, and the model ages obtained range from 91. 5±1.3 Ma to 92.3±1.3 Ma, with an isochron age of 90.6±2.1 Ma and a weighted mean age of 91. 8±0.5 Ma, indicating that the mineralization of the Larong deposit occurred at the Late Cretaceous. The Re content of molybdenite ranges from 53.0×10-6 to 86.1×10-6, suggesting that the metallogenic material originated from a crust- mantle mixed source. The metallogenic age of the Larong W- Mo deposit indicates that the Later Cretaceous tungsten polymetallic mineralization event occurred in the Leiwuqi- Zuogong metallogenic belt in the northeastern section of Bangonghu- Nujiang tectonic belt, with mineralization occurring in the Lhasa- Qiangtang collisional orogenic setting.