After a detailed field geological investigation, writers analysed the sulfur and lead isotopic compositions of the ores, oxygen isotopic compositions of quartz and hydrogen isotopic compositions of the inclusions in the quartz from the ore bearing quartz veins, and rhenium content of the molybdenite in the Dayinjian molybdenum deposit, Xinxian County, Henan Province; discussed the ore forming material resource and ore forming mechanism. The δ34SV CDT values of the ores range from 390‰ to 1070‰, with an average value of 744‰; n(206Pb)/n(204Pb), n(207Pb)/n(204Pb) and n(208Pb)/n(204Pb) ratios of the ores range from 1704 to 1732, 1540 to 1542 and 3773 to 3824, respectively. The δ18OSMOW， SymboldA@ D SMOW, and δ18OH2O，SMOW of the ore bearing quartz precipitated in the main mineralization stage are 11.20‰～13.20‰（with an average 11.90‰）, -79.00‰～-76.90‰ （with anaverage value of -78.28‰），and -0.26‰～3.70‰（with an average value of 1.82‰）, respectively, which show the characteristics of oxygen isotope drift. The contents of rhenium in the molybdenite range from 8.28×10-6 to 54.74×10-6. The sulfur isotopic compsition indicates that the ore sulfur mainly came from magma in deep source and contaminated by the crustal substances; lead isotopic composition of ores and rhenium content in the molybdenites showed that ore forming materials come from the crust; and hydrogen, oxygen isotopic compositions suggests a mixing between magmatic hydrothermal and meteoric water in the late mineralization stage. Therefore, the composite action is proved to be the Dayinjian molybdenum deposit formed an important ore foreming mechanism.