In order to solve the problems that it is difficult to adapt to the complex working environment of PRESSURIZED WATER REACTOR nuclear power unit, the feedwater flow control is unstable, and it is difficult to achieve accurate regulation, a feedwater flow control method for PRESSURIZED WATER REACTOR nuclear power unit based on nonlinear state generalized prediction is proposed. The method comprises the following steps of: acquiring historical data of feedwater flow by using a differential pressure type flowmeter; predicting the feedwater flow at a future moment by using a nonlinear state generalized prediction model on the basis of the historical data; calculating an error compensation quantity by taking an error between a prediction result and a current acquisition result as an input; and controlling the feedwater flow of the pressurized water reactor nuclear power unit through a control law of a controller. The results show that the method can control the feedwater flow efficiently in the uncertain environment, and the control error is relatively smaller and the control performance is better.