Abstract: Based on the principle of human factors engineering（HFE）, this paper takes the secondary feed water deaerator system of a nuclear power plant as an example to analyze the performance requirements, obtain different levels of static function database, and determine the basic information flow and its processing requirements. In order to meet the operational requirements of the nuclear power plant in the cold start, the low load and high load conditions and the functional factors related to the control room are clarified by establishing the water supply heating and deaeration function (F01) block diagram and operation mode table. Based on the principle of functional allocation, the water level control of the deaerator is studied, and the non - disturbance transition scheme of water level control is realized. It has been verified by human - machine interface design, and provides reference for the human factor engineering analysis in China.