[en] The optimal maintenance of safety systems is one of components, which insure reliable and safe operation of nuclear power plants. The optimal service interval depends on the composition and structure of system and is unique for each safety system. So matching and determination of a common periodicity of safety systems maintenance are required. The method for optimizing the periodicity of safety systems maintenance based on a risk-oriented approach and PSA results is presented. As a criterion of system importance proposed the calculated indicator - interval of risk reduction. An example of implementation of the method is considered and recommendations for its application are given. Keywords: maintenance, safety systems, service interval, risk-oriented, PSA, NPP.