Abstract: The main control room (MCR) temperature and humidity control system of nuclear power plant has major capacity lag and some interference factors. In order to meet the human factor requirements of MCR’s operators and the control panels’environmental requirements, the improved temperature and humidity control scheme was designed based on the provided temperature cascade control system and the humidity cascade control system. In order to overcome the PID controller’s shortcoming heavily depending on the accurate mathematical model, an intelligent PID parameter setting method was provided with the improved particle swarm optimization (PSO) algorithm.