Abstract: In order to solve the problems of existing simplified correlation analysis assumptions of seismic probabilistic safety assessment (PSA), and establish methods that more accurately reflect the seismic correlation of structures, systems, and components (SSC) of nuclear power plant, correlation analysis of fragility based on separation of variables was studied. Theoretical derivations of the method were carried out with the fragility model, and the implementation process of the method was introduced. Case studies on joint failure of SSCs under different conditions using proposed method were carried out, and the fragility curves and frequencies of joint failure were obtained, which were compared with the results obtained by the existing simplified methods. The results show that the seismic PSA correlation analysis method based on separation of variables can make up for the deficiencies of existing methods and support the development and application of seismic PSA for nuclear power plants.