Abstract: A code (NEPMR) was developed for dynamic simulation of electrical heating pressurizer. Nonequilibrium multiregion model was considered and Gear method was adopted for numerical solution. The calculation results were compared with the test results of transient loss of load from 74 MW and 105 MW for Shippingport Nuclear Power Plant in America, and the trend showed a good agreement. The NEPMR program can well reflect the thermal stratification phenomenon of control volumes in the pressurizer during transient loss of load process. At the moment of the pressurizer sprayer on and off, a flow rate jump phenomenon occurrs at the interfaces between volumes of vapor and liquid phase. The computed results prove the applicability and accuracy of nonequilibrium multiregion model and the program simulation.