Radioactive waste gas treatment system of the Hualong One Innovative Pressurized Water Reactor is designed by analyzing the volume and characteristics of the upstream waste gas and adopting the “activated carbon pressurized retention decay” technology for treatment. The system operation parameters are determined through performance bench tests; meanwhile, a hydrogen-oxygen recombiner is introduced in the explosion-proof design to eliminate hydrogen from the source. The final design of the radioactive waste gas treatment system can meet the requirements of radioactive waste gas treatment and ensure the compliance of gaseous effluents. Compared with the waste gas treatment technologies of different reactor types, it is found that the waste gas treatment process of the Hualong One Innovative Pressurized Reactor has the advantages of smaller floor space, better treatment effect, less waste activated carbon generation, and improved safety performance.