Abstract: Based on a nuclear power plant in China and the assess principle of the Regulatory Guide 1.78-Evaluating the Habitability of a Nuclear Power Plant Control Room during a Postulated Hazardous Chemical Release, the U.S. nuclear safety guide, we collected and screened the chemicals used in this project, and use ALOHA to calculate the concentration of toxic and hazardous gases entering the main control room when a leak occurs. Finally, the impact of the leakage on the habitability of the main control room is evaluated. The simulation results show that, since the nuclear island is enclosed and the air vents of the main control room is inside of the nuclear island, when a toxic and hazardous gases leak occurs, the concentration of toxic and hazardous gases near the air vents is lower than the limits, and will not have a significant impact on the habitability of the main control room.