Abstract: The radiolytic degradation process of carbendazim was investigated by γ-irradiation. The effect of the initial condition of irradiated solution on the effectiveness of carbendazim decomposition was studied, and the degradation products were identified by LC-MS, additionally, quantum chemistry was used to analyze the degradation pathway of carbendazim. The results indicate that carbendazim can be degraded efficiently, the lower the initial concentration of carbendazim is and the higher the absorbed dose is, the better the degradation rate of carbendazim is. The contribution to carbendazim degradation by the radicals is in the order of •OH>•H>e^-_aq. Three main degraded products (m/z=119, 134 and 208) were identified by LC-MS. Bond orders, bond lengths and NBO atomic charges of carbendazim are highly in accordance with those of LC-MS identification. According to combination of parameters of carbendazim and LC-MS identification, the pathway of carbendazim degradation is that 5-hydroxycarbendazim, 2-aminobenzimidazole and benzimidazole are produced by free radicals reacted with carbendazim, then small molecules are produced by free radicals reacted with 2-aminobenzimidazole and benzimidazole.