Abstract: Chehugou Mo-Cu deposit is a typical porphyry Mo-Cu deposit in the Xilamulun molybdenum metallogenic belt on the northern margin of North China Craton (MNCC). It locates to the south of the MNCC fault. The orebodies are mainly hosted in granite porphyry. The Mo mineralization is characterized by veinlet-disseminated mineralization as well as breccia type and quartz vein type mineralization. According to crosscutting relationships of different veins and mineral parageneses, ore-forming process can be divided into four stages: (1) the pyrite-molybdenite-quartz stage; (2) the pyrite -chalcopyrite-quartz±molybdenite stage; (3) the pyrite-quartz stage; and (4) the quartz-carbonate±fluorite stage. Petrographic study of fluid inclusions suggests that six dominant types of fluid inclusions related to metallogensis are present in the deposit: Ⅰ-Type CO2-bearing three-phase (LCO2+VCO2+LH2O), Ⅱ-Type daughter-minerals bearing three-phase (V-L+S), Ⅲ-Type gas-rich (V-L), Ⅳ-Type liquid-rich (L-V), Ⅴ-Type pure gas (V) and Ⅵ-Type pure liquid (L) phase inclusions. Types of fluid inclusions regulary evolves from the early stage to the late stage. Fluid inclusions in the first and the second stage are characterized with Ⅰ-Type CO2-bearing three-phase (LCO2+VCO2+LH2O) and Ⅱ-Type daughter-minerals bearing three-phase (V-L+S) inclusion. But in the later the third and the fourth stage which are characterized with Ⅲ-Type gas-rich (V-L) and Ⅳ-Type liquid-rich (L-V) inclusion. Homogenization temperatures and salinities of ore-forming fluid also regularly evolves from the early stage to the late stage. The peak value of Homogenization temperatures of different stages are separately 270~400℃, 230~370℃, 160~290℃, 120~230℃, showing a reducing tendency from the early stage to the late stage; Fluid salinities of the first stage could subdivide into two groups: 3.39%~14.25% NaCleqv and 31.01%~＞66.75% NaCleqv. Fluid salinities of the second stage also could be subdivided into two groups: 1.23%~12.85% NaCleqv and 31.14%~64.33% NaCleqv. Fluid salinities of the third and the fourth stage are separately 1.05%~21.47% NaCleqv and 2.07%~10.73% NaCleqv, which is showing a reducing tendency. Laser Raman spectroscopic and inclusion groups components studies indicate that components of ore-forming fluid mostly contains H2O, CO2, Cl-, SO42-, Na+ and minor F-, Ca2+, Mg2+. Diagnostic ion ratios indicates that ore-forming fluid is derived from magmatic fluid. Petrographic and microthermometric study indicate that the early first and the second stage high temperature, high salinities, CO2-bearing NaCl-H2O-CO2 system ore-forming fluid occurs boiling and phase separation. With fluid boiling, CO2 escaping and temperature decreasing, abundant metal sulfides precipitate. In the later third and fourth stage, ore-forming fluid system tends to open when atmospheric condensation interfuses into the system; ore-forming fluid evolves to middle-low temperature, middle-low salinitie and CO2-poor NaCl-H2O system. Boiling characterized the early ore-forming stage which leads to the precipitation of molybdenite and chalcopyrite, while in the later third and the fourth ore-forming stage fluid mixing is the leading minerogenesis mechanism.