Theoretical simulation of the adsorption and dissociation of two NO molecules at the Cu2+, Cr3+ and bridge Cr3+ sites (b-Cr3+) on the normal spinel CuCr2O4 (100) surface has been carried out by density functional theory calculations. The results show that the formed N-down and O-down NO dimers are negatively charged. The formation of stable O-down dimers on the surface leads to the great elongation of N-O bond, which contributes to the NO reduction. The transition-state calculations indicate that the decomposition of O-down NO dimer at the b-Cr3+ site is most favorable and N2O is the major reduction product. Theoretical simulation of the adsorption and dissociation of two NO molecules at the Cu2 +, Cr3 + and bridge Cr3 + sites (b-Cr3 +) on the normal spinel CuCr2O4 (100) surface has been carried out by density functional theory calculations. N-down and O-down NO dimers are negatively charged. The formation of stable O-down dimers on the surface leads to the great elongation of NO bond, which contributes to the NO reduction. The transition-state calculations indicate that the decomposition of O-down NO dimer at the b-Cr3 + site is most favorable and N2O is the major reduction product.