Abstract: The excessive oxidation on the surface of micro−fine molybdenite and the dissolution behavior of the surface oxidation products are not favorable for molybdenite flotation, for this reason, sodium sulfate was used to reduce the degree of surface oxidation of fine−grained molybdenite and inhibit the dissolution of surface oxidation products in order to improve the flotation efficiency of molybdenite. The results indicated that the appropriate amount of sodium sulfate could reduce relative content of Mo−O bonds on the surface of micro−fine molybdenite, which had a certain regulatory effect on the oxidation reaction of micro−fine molybdenite and the dissolution process of oxidation products. Sodium sulfate at 0.08 mol/L reduced the sulfate ion concentration in the slurry by 68.25% and the dissolved oxygen concentration by 25.81%, and reduced the crystalline spacing of the micro−fine molybdenite (100) crystal faces, while increasing the crystallinity. Secondly, the sulfate ions ionized by sodium sulfate in solution produce a common ion effect on the dissolution reaction of sulfur oxidation products on the surface of molybdenite, which hindered the dissolution of oxidation products and improved the uniformity and floatability of fine−grained molybdenite surface properties. The study has certain guiding significance for the regulation of the oxidation−dissolution process of micro−fine molybdenite and its flotation effects improvement.