Abstract:NH3-SCR de-NOx technology has been widely used due to its good efficiency and stability, and its core is catalyst. γ-Fe2O3 is a catalyst with good activity at low temperature, and its performance can be effectively improved by doping with Cu. In order to explore its reaction mechanism, the adsorption behavior of NH3, NO, and O2 on γ-Fe2O3 catalyst surface was studied based on Density Function Theory (DFT). The results show that NH3 NO and O2 are adsorbed on Cu and Fe active sites and formed stable adsorption configurations. In the process of NH3 adsorption, NH3 will lose electrons, and N atoms form stable chemical bonds with Fe and Cu. When NO atom is close to the catalyst surface with N atom end, chemical adsorption mainly occurs, while physical adsorption occurs when NO atom is close to the surface with O atom. NO is mainly characterized by the loss of electrons and the formation of stable chemical bonds when adsorbed by N atoms. When O2 is adsorbed, it will get electrons and form a stable chemical adsorption configuration with metal ions. During the adsorption process, small molecules are relatively stable when adsorbed on the active site of Fe.