Abstract: The Jiama super-large copper polymetallic deposit has molybdenum resources in excess of one million tons, and molybdenite is the most important molybdenum mineral. Rare earth elements (REEs) and trace elements of molybdenite from different stages were analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) in order to understand the source and nature of ore-forming fluids. Molybdenite contains REE contents ranging from 39.34 to 168.1 μg/g, which is similar to those of porphyry and skarn deposits at Jiama. From early to late stage, REE contents of molybdenite increase and light rare earth elements are relatively enriched, indicating the ore-forming fluids might be derived from magma. Molybdenite shows REE patterns with negative Eu and Ce anomalies, and positive Sm anomaly. Negative Eu anomaly suggest that the ore-forming fluids are relatively reduced. Molybdenite contains high Cu, Pb, Zn, Bi indicating the enrichment of these elements in fluids.