The invention discloses a radioactive waste gas processing device for a nuclear power station. The radioactive waste gas processing device comprises a silica gel drying bed and activated carbon retention beds. The silica gel drying bed is connected with a radioactive waste gas pipeline at the upstream part for drying radioactive waste gas. The activated carbon retention beds are connected to the downstream part of the silica gel drying bed. By utilization of selective absorption effect of activated carbon, radioactive inert nuclides in waste gas are subjected to dynamic absorption and retention such that inert nuclides are fully decayed for reducing the radiation level. Compared with a conventional radioactive waste gas processing device, the radioactive waste gas processing device for the nuclear power station has following beneficial effects: by utilizing combination of the silica gel drying bed and the activated carbon retention beds, radioactive waste gas is effectively processed; the silica gel drying bed can be used for controlling humidity of waste gas to the lower level in order to improve absorption performance and prolong service lifetime of activated carbon; the activated carbon retention beds are used for dynamically absorbing inert nuclides such that inert nuclides are subjected to retention and decay; the radiation level is decreased; system safety and operation convenience of the overall processing device are enhanced; and space appropriation amount is increased.