The Chang’an gold ore deposit in western Yunnan is located at the southern segment of the Ailaoshan metallogenic belt. The ore bodies are preserved in fractured Ordovician sedimentary clastic rocks. The gold-bearing minerals occur dominantly in sulfide-quartz veins. Fluid inclusion analysis shows that the Chang’an gold ore deposit is characterized by epithermal gold mineralization at temperatures between 200°C and 280°C at a shallow crustal level. The mineralizing fluids have intermediate to low salinity (6%-18%) and low densities (0.72-1.27 g/cm3). The ore minerals have δ34S in a range from -13‰ to 3.57‰, concentrated from -2.06‰ to 3.57‰ with an average of 1.55‰. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values are 18.9977-19.5748, 15.7093-15.784, 39.3814-40.2004 respectively. These isotope data suggest that the ore-forming elements were mainly derived from mixed crustal and mantle sources. The Chang’an gold ore deposit and Tongchang Cu-Mo deposit are closely related to each other in their spatial distribution and age of formation. They have similar sources of mineralizing elements and identical ore-forming metal elements, and show a close relationship in physical and chemical conditions of mineralization. The two deposits constitute an epithermal-porphyry-skarn type Cu-Mo-Au mineralization system in the Tongchang-Chang’an area, which is related to the Cenozoic high-K alkaline magmatism.