Located in the northeastern Zijinshan ore field, the Luoboling Cu-Mo deposit is a large –scale porphyry deposit hosted by Sifang granodiorite and Luoboling granodiorite porphyry. Re-Os dating of eleven molybdenite separates collected from different depths of ore bodies in the Luoboling Cu-Mo deposit shows that the isochron age is 104.9±1.6Ma and the model ages range from 104.7±1.6 Ma to 106.5±1.5Ma, with an average age of 105.64±0.46Ma. It indicates that the Luoboling Cu-Mo deposit was formed in Early Cretaceous, consistent with the emplacement age of the host rocks, and that the magmatism and mineralization took place under the same geological setting. Since the Zijinshan ore field is composed of several porphyry and epithermal deposits, it is suggested that the ore fluid evolution of Zijinshan ore field may started from 105Ma, when the Luoboling porphyry Cu-Mo deposit was formed.