Abstract: The Jinduicheng Porphyry Molybdenum Deposit, Shanxi Province is one of the largest molybdenum deposits in China. Base on the observation of the cross-cutting sequence of veins, the whole ore-forming process can be divided into two periods and ten stages. The analysis of fluid inclusions in quartz indicates that the ore-forming hydrothermal system is rich in CO2. The average homogenization temperature ranges from 83 to 412℃. The salinty of metallogenetic fluid manifests bimodal distribution pattern with two ranges from 27.5 to 42.5 wt％ NaCl and from 0.61 to 17 wt％ NaC1 equiv. The values of oxygen and hydrogen isotope show that the major source of metallogantic element is magmatic fluid. At the last stage large amount of meteoric water was mixed into the hydrothermal system, leading to decrease of temperature, salinity, δ18OH2O andδD, and to precipitation of molybodnite which formed the main body of the super-large Jinduicheng molybdenum deposit.