The Tianshan-Xingmeng molybdenum belt is part of a larger E-W trending metallogenic belt in northern China. Most of the molybdenum deposits occur as porphyry or porphyry-skarn type, but there are also some vein type deposits. Following systematic Re-Os dating of molybdenite from 4 deposits and comparisons with two previously dated deposits, we have inferred that the molybdenum mineralization in the Tianshan-Xingmeng orogenic belt was developed during hydrothermal activity linked to magmatism and the emplacement of granitoid stocks. Three pulses of granitoid magmatism and Mo mineralization have been recognized in this study, corresponding to significant tectonic events in the Tianshan-Xingmeng orogenic belt. Our results show that the Late Paleozoic Cu-Mo deposits are closely related to subduction-accretion generated lithosphere processes, whereas the Triassic Mo deposits probably formed in a syn-collision setting between the Siberian and Tarim-North China Cratons. Similarly, the Jurassic-Early Cretaceous Mo deposits are most likely related to tectonic and magmatic events resulting from the westward subduction of the palaeo-Pacific plate.