Reported in this paper are Cu isotope compositions of sulfides and bulk samples of quartz-monzodiorite stock and wall-rock from Donggushan porphyry-skarn deposit in the Middle-Lower Yangtze valley. A large variation in δ65Cu values from -0.54‰ to 0.95‰ (ca.1.5‰) has been observed, indicating significant Cu isotope fractionation occurs during high-temperature metallogeny. Systematic zonation of Cu isotopes is observed in chalcopyrites from different positions. Outward from stock, Cu isotopic compositions become heavier progressively. This Cu isotopic zonation can be resulted during metallogeny processes. For the case of Dongguashan deposit, the Cu isotopic zonation cannot be explained by isotope fractionation of Cu between vapor and solution but by isotope fractionation between sulfides and fluid during minerals precipitation processes. Sulfides incorporating heavy light isotopes preferentially leave the fluid enriching in heavy isotopes. Precipitation of suilfides results in the Cu isotope composition of residual fluid evolving with time. Cu isotope composition of sulfides can be used to trace the path of ore-forming fluid.