Abstract: In this paper, based on an analysis of ore-forming geological conditions of the Dapai iron-lead-zinc polymetallic deposit in southwestern Fujian, the authors chose magnetite and garnet to analyze oxygen isotopic compositions and pyrite, sphalerite and galena so as to determine sulfur and lead isotopic compositions. Studies show that the δ18O values of garnet vary from 3.4‰ to 6‰, indicating that the oxygen isotopic compositions of garnet skarn might have inherited those of the concealed granite body. The oxygen isotopic compositions of magnetite were used to calculate the δ18O values of the ore-forming fluid at the magnetitization stage. They were 9.23‰~11.34‰ at the assumed temperature of 500℃ or 8.58‰~10.69‰ at the assumed temperature of 600℃ respectively. These data indicate that the 18O-enriched CO2 was dissolved in the ore-forming fluid. The δ34S from ore sulfides has a small range of -2.6‰~1.5‰, the distribution of values is around the zero, (0±3‰) , a characteristic that implies a magmatic sulfur. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of sulfide ores vary in the ranges of 18.486~18.537, 15.665~15.712 and 38.823~38.979 respectively. The lead isotopic ratios vary in a small range. A comprehensive analysis of the lead isotopic data indicates that the metallogenic materials of this deposit were closely related to magmatism, which was mainly derived from the lower crust with a bit crust-mantle mixing. In combination with Makeng style iron polymetallic deposits of southwestern Fujian and chronologic discussion on Mesozoic granites in southwestern Fujia, the authors hold that the formation of the Dapai iron-lead-zinc polymetallic deposit had connection with intrusion and metasomatism of Mesozoic granites. The above understanding has important theoretical significance for determination of prospecting direction of iron polymetallic ores in southwestern Fujian Province.