The invention relates to a parameter acquisition method for a primary loop system of a pressurized water reactor. The model parameter acquisition method comprises the steps of combining the characteristic that the pressurized water reactor is complicated in model structure, provided with nonlinear links, long in stable transition time, great in number of model parameters and variables, mutual coupling and the like, recognizing model parameters by adopting submodules, and checking the parameters by adopting an overall model; selecting input and output variables of each module to perform testing; reducing influences imposed on a recognition effect by noise signals through preprocessing; initializing the variables based on a differential equation of each module and a program setting method, and enabling the model to be stable in initialization; recognizing parameters of each module based on a parameter perturbation theory and an intelligent optimization method; checking the parameters and the model under various conditions by combining the submodules and the overall module; and acquiring nuclear power unit system mathematic model parameters applicable to electric power system analysis. The modules are fine and clear in structure, the model parameters are definite in meaning, the variables required by recognition are easy to acquire, the parameter acquisition method is quick, efficient and accurate, and the practicability is high.