The main function of the modular small reactor component cooling water system (WCC) of Linglong is to cool the users who need component cooling water in each building. The system uses seawater to cool the circulating water through the heat exchanger, which ensures the stable and efficient operation of the Nuclear Power Plant (NPP), so the reasonable design of the heat exchanger becomes extremely important. Plate heat exchanger (PHE) is known for its compact structure, high heat-transfer efficiency and easy maintenance, and is often used in the component cooling water system of equipment. In order to verify the performance of the equipment supplied by the manufacturer, several conventional methods were used to check and verify the plate heat exchangers in Fuqing Unit 3 and 4. The results show that the deviation between the heat-transfer area calculated by the Criterion Number Method and the manufacturer's design value is the smallest. In this paper, the Criterion Number Method is used to verify the plate heat exchanger used in Linglong. Through detailed analysis and calculation, it is finally proved that the heat exchanger supplied by the manufacturer meets the engineering requirements in terms of heat-transfer and ensures the safe and stable operation of the component cooling water system. This study has important reference value and significance for equipment selection, design optimization and performance verification of similar nuclear power projects in the future.