Abstract: Kumutage molybdenum deposit locates to the southeastern side of Kumutage sand ribbon, Hami area, Xinjiang. It is the first molybdenum deposit by far which molybdenite occurs in the basic rocks. Seven orebodies had been found in the district. All of them distribute around the arc contact zone between gabbro and hornstone/skarn. The main metal minerals are molybdenite, chalcopyrite, pyrite, magnetite, and so on. The molybdenite and chalcopyrite have the shape of sparse disseminated in the gabbro. This paper dates the age of molybdenite by Re-Os method. We obtain the isochron age of (318±27)Ma and the weighted average age of (319.1±4.5)Ma. These results imply that this deposit formed at Early-Middle Carboniferous. This age accorded with the intrusion time of granite in this area. So we infer that the metallogenesis is related with the activity of acid rocks in central Tianshan massif. The contact zone between acid rocks and intermediate to basic rocks is the favourable section for looking for this new type deposits. The discovery of Kumutage has important significance. Because it not only challenged to prospecting model for molybdenum deposits but also extended the prospecting ideas in the basement of eastern Tianshan.