According to the needs of domestic nuclear power development, a single type of reactor coolant pump can no longer meet the requirements of nuclear power batch construction. Conducting an analysis of the impact of key parameters of reactor coolant pump replacement, exploring the applicability analysis method of reactor coolant pump selection, and selecting a reasonable and reliable main pump have become the top priority for nuclear power development. Research has shown that key parameters such as the rotational inertia, friction torque, and four quadrant curve of the reactor coolant pump fall within the safe range, which can determine the safe operation of the unit under accidents. This article takes a million kilowatt nuclear power plant as the research object, determines the key parameters that need to be considered for the selection of the reactor coolant pump and the corresponding applicable range of the parameters. Based on this, three models of reactor coolant pump that meet the applicable range are selected, and the rationality of the selected reactor coolant pump model number is determined through typical accident impact analysis.