Abstract: In this paper the reaction cross sections of H+O_2(n_0j_o)→HO+O and C+H_2(n_0j_0)→NCH+H systems with long-lived complex on their ab initio potential energy sur- faces were calculated using Marcus′ Microcanonical Transition State Theory. Ef- fects of the properties of potential energy surfaces on the reaction cross sections were discussed. We found that the reaction cross sections of the two systems first increase and then decrease as collision energy increases at given vibrational-rota-tional quantum number (n_0j_0), except n_0=0 and j_0=1; the reaction cross sections of the two reactions are all increased obviously with increase of n_0 at given collision energy and internal rotational state j_0; the variation of the reaction cross sections is complicated with increase of j_0 for H+O_2 system, and monotonous for the C+H_2 system except j_0=1. These calculated results of the reaction H+O_2(n_0j_0)→HO+O are in good argreement with that obtained by Quasiclassical Trajectory Theory and the experimental measurement.