Abstract: Defects in crystal structure of pyrite,which could change the oxidation mechanism and process,will affect the surface properties,and then makes the flotation behavior different.This paper study defects' existence and diffusion law from its microstructure,analyze its impact on the oxidation mechanism of pyrite surface;investigate the oxide elements' form of existence on the surface of pyrite by XPS test technology,and analyze its impact on the surface properties.The results show that:O₂ molecules do not directly participate in the chemical reaction,but by HO₂·and OH·free radicals which can catch the electrons of Fe²⁺ ions to achieve chemical adsorption.The defects and charged particles in the oxidation membrane carry on directional migration in the influence of chemical potential and electrochemical potential gradient,which promote the oxidation reaction and improve pyrite surface's hydrophilicity.The results of X-ray photoelectron spectroscopy analysis confirm the crrrectness of the inferred oxidation mechanism.