The decontamination solution produced by the primary circuit decontamination process of the PWR nuclear power plant contains a large number of radionuclides, mainly 58Co and 60Co. In order to reduce the radiation dose in the decontamination environment and avoid the secondary deposition of radionuclides, it is necessary to effectively remove the radioactive cobalt (Co) in the decontamination solution. In view of the adsorption performance of uniform particle size cation resin (G-resin) for cobalt in simulated decontamination solution, this paper mainly explored the adsorption of G-resin for cobalt in simulated decontamination solution under different simulated experimental conditions, different adsorption time, different initial concentration of Co2+, interference ions, irradiation dose and cycle number. The results show that the adsorption process of Co2+ in the simulated decontamination solution by G-resin conforms to the pseudo-second-order kinetics and Langmuir adsorption isotherm model. The adsorption equilibrium can be reached within 120 minutes, and its maximum adsorption capacity can reach 74.91 mg g−1. Meanwhile, G-resin also has good adsorption selectivity and radiation stability. G-resin is expected to be applied to the removal of radioactive cobalt in the decontamination solution of nuclear power plants.