Taking four nuclear power plants to be built in Guangdong and Fujian Coastal Area as examples, based on the seismic zoning map of China (GB18306-2015), the synthetic earthquake sequences are simulated by Monte Carlo method, and the ground motion parameters of each nuclear power plant site are obtained through attenuation relationship. By calculating the probability that multiple nuclear power plants would be affected by earthquakes that would exceed the fortification criteria at the same time, the seismic hazard correlation among nuclear power plants is quantitatively analyzed. This method can be used as a supplementary work for the site selection of nuclear power plants to improve the seismic performance of nuclear power plant cluster.