Systematic geochronological study on the petrogenetic and metallogenic ages of the Machangqing porphyrytype copper—molybdenum—gold orefield, western Yunnan, reveals: zircons from syenite porphyry yield a UPb age of 356±03 Ma; zircons from granitic porphyry yield a UPb age of 350±02 Ma; zircons from the porphyritic granite yield a UPb age of 3393±038 Ma; molybdenites of Machangqing porphyrytype copper—molybdenum mineralization(from Baoxingchang ore section )yield a ReOs isochron age of 358±16 Ma and 339±11 Ma; muscovites from skarntype gold mineralization of Luandongshan ore section yield an ArAr plateau age of 3525±036 Ma and an isochron age of 350±036 Ma; Muscovites from altered tectonitetype gold mineralization of Rentouqing—Jinchangqing ore section yield an ArAr plateau age of 3535±032 Ma and an isochron age of 3444±099 Ma. And, the Machangqing porphyrytype mineralization whose age is 358 Ma has a close spatial relationship with syenite porphyry and granitic porphyry, and its age is nearly the same as Luandongshan skarntype gold mineralization(350 Ma) and Rentouqing—Jinchangqing tectonitetype gold mineralization(3444 Ma). The porphyrytype mineralization whose age is 339 Ma shows close spatial associations with porphyritic granite whose age is 3393 Ma. All above reflect that theⅡperiod magmatic combination whose emplacement age is from 33 to 36 Ma,consisting of syenite porphyry+monzonite porphyry+granitic porphyry+ porphyritic granite, is the oreforming geological body and supplies materials, fluid and dynamic for copper—molybdenum—gold mineralization. The porphyrytype copper—molybdenum mineralization whose age is 358 Ma, Luandongshan skarntype gold mineralization and Rentouqing tectonitetype gold mineralization form at the early—middle stage of Ⅱ period magma activity. The porphyrytype copper—molybdenum mineralization whose age is 339 Ma is related to the late stage porphyritic granite. The duration of magmatichydrothermal system of Machangqing ore concentration area is about 3 Ma.