The NO 2+NO - 2 electron transfer reaction was studied with DFT B3LYP method at 6 311+G * basis set level for the eight selected structures: four species favor the structure of “head to head”. The geometry of transition state was obtained by the linear coordinate method. Three parameters, non adiabatic activation energy ( E ad ), coupling matrix element ( H if ) and reorganization energy ( λ ) for electron transfer reaction can be calculated. According to the reorganization energy of the ET reaction, the values obtained from George Griffith Marcus (GGM) method (the contribution only from diagonal elements of force constant matrix) are larger than those obtained from Hessian matrix method (including the contribution from both diagonal and off diagonal elements), which suggests that the coupling interactions between different vibrational modes are important to the inner sphere reorganization energy for the ET reactions in gaseous phase. The value of rate constant was obtained by using above three activation parameters. The NO 2 + NO - 2 electron transfer reaction was studied with DFT B3LYP method at 6 311 + G * basis set level for the eight selected structures: four species favor the structure of “head to head”. The geometry of transition state was obtained by the linear coordinate method. Three parameters, non adiabatic activation energy (E ad), coupling matrix element (H if) and reorganization energy (λ) for electron transfer reaction can be calculated. According to the reorganization energy of the ET reaction , the values ​​obtained from George Griffith Marcus (GGM) method (the contribution only from diagonal elements of force constant matrix) are larger than those obtained from Hessian matrix method (including the contribution from both diagonal and off diagonal elements), which suggests that the coupling interactions between different vibrational modes are important to the inner sphere reorganization energy for the ET reactions in gaseous phase. The value of rate co nstant was obtained by using above three activation parameters.