Abstract: The ore-forming fluids of Donggou Mo deposit physical-chemically changed from high temperature and salinity of the earlier stages to low temperature and salinity of the later stages.The mineralization pressure and depth of the quartz-molybdenite stage are from 18 to 95MPa and from 0.7 to 3.7km.The low content of CH₄ and C₆H₆,and the oxygen fugacity,pH values and Eh values decreased from early stage to the late stage,suggesting a weak reducing environment when the Mo elements precipitating.The boiling of the fluid may change the physicochemical properties of ore-forming fluid and resulted in the precipitation of Mo.