Abstract: The Tongcun porphyry molybdenum deposit is located in the east section of the Qinzhou-Hangzhou metallogenic belt, close to the large-scale mineralized concentration area in northeastern Jiangxi Province. The formation of the deposit is related to the syntecticgranite which invaded in the early Yanshan period. The mineralization age of the granite is 165-168Ma. The disseminated molybdenite occurs in the contact zone between the intrusion and alteration zone. Re-Os isotopic age of the three molybdenite samples was measured for the first time, yielding 187Re-187Os isochron age of molybdenite as 161.8±2.2Ma(MSWD=0.006), representing the mineralization age. The ore-forming age is concordant with the rock-forming age, and the deposit is of porphyry-skarn-type molybdenum ore deposits.