The invention relates to a dynamic modeling and analysis method for a nuclear power unit coolant shield main pump. A coolant main pump flow calculation model is established based on the influence of the power grid side voltage and frequency on the main pump and the characteristics of a shield motor; based on a main pump motor electromagnetic torque formula, in consideration of the friction torque of the coolant main pump, the resistance torque of the whole main pump motor system is calculated; based on the running characteristics of an asynchronous motor, the coolant main pump electromagnetic torque is solved, and thus the coolant main pump flow calculation model for power system analysis is established; according to existing design and test data, parameter identification is conducted to identify the corresponding parameters in the model. According to the dynamic modeling and analysis method, the friction torque of the coolant main pump is considered, the influence of the power grid side voltage and frequency fluctuation on the coolant flow can be accurately reflected in real time, the influence of the power grid fluctuation on nuclear power safety is accurately analyzed accordingly, the defect that most present main pump coolant analysis centers on main pump idling and main pump jamming analysis is overcome, and the method has higher real-time performance for nuclear power analysis of connected grids.