Risk-informed safety classification of structures, systems and components (SSCs) is very important forensuring the safety and economic efficiency of nuclear power plants (NPPs). However, previous methodsfor safety classification of SSCs do not take the plant operating modes or the operational process of SSCsinto consideration, thus cannot concentrate on the safety and economic efficiency accurately. In thiscontribution, a new method for safety classification of SSCs based on the categorization of plant operating modes is proposed, which considers the NPPs operating history to improve the economic efficiencies while maintaining the safety. According to the time duration of plant configurations in plantoperating modes, average importances of SSCs are accessed for an NPP considering the operationalprocess, and then safety classification of SSCs is performed for plant operating modes. The correctnessand effectiveness of the proposed method is demonstrated by application in an NPP's safety classificationof SSCs