The reaction mechanism of FC(O)O radical with NO2 was studied by means of quantum chemical methods. The geometries for all the stationary points on the potential energy surfaces were optimized fully at the B3LYP/6-311 + + G(3df, 3pd), MP2/6-311 + + G**, G3 and G3MP2 levels, respectively. All the transition states were verified by the intrinsic reaction coordinate (IRC) calculations at the B3LYP/6-311 + +G (3df, 3pd) level. The reaction coefficients for the elementary reactions were calculated by transition states theory (TST).