Abstract: The Wulandele molybdenum-copper polymetallic deposit in Sonid Left Banner of Inner Mongolia is a large deposit dis-covered recently during the geological survey in the Erlian-Dong Ujimqin Banner metallogenic belt of Inner Mongolia. Ore geology characteristics show that the formation of the molybdenum-copper polymetallic deposit had spatial-temporal and genetic relation-ships with the concealed fine-grained monzonitic granite in this area. In order to reveal the metallogenic regularity in this area, the authors determined the SHRIMP single particle zircon U-Pb age of the fine-grained monzonitic granite. The results show that the weighted average ²⁰⁶Pb/²³⁸U age of 131.3±1.6Ma(MSWD=1.7)is consistent with the molybdenite Re-Os age of 134.1±3.3Ma, sug-gesting that the formation age was Early Cretaceous. The result of geological exploration shows that the formation of the deposit was closely related to the concealed Yanshanian fine-grained monzonitic granite. The result of isotopic dating is important for the study of the regularity of ore formation.