Based on analyzing the isolation status of the fire protection system in a nuclear power plant, multiple new technologies such as informatization, and big data are applied to develop a set of auxiliary evaluation on digital isolation of fire protection system in the nuclear power plants, which realizes online structured modeling and automatic generation of fire protection system structure charts, sets up a isolation boundary database, and establishes the optimal isolation chart or isolation plan, calculation of the fire protection system availability, and update and display of fire protection system isolation status, which solves the problems of false isolation, less isolation and misunderstood isolation due to the diversity, complex logic, multiple points and wide coverage of fire protection system equipment as well as the inconsistent drawings of multiple design institutes, offers technical support for the correctness of operation and maintenance personnel, reduces human errors, realizes the visualized, and refined isolation of fire protection system, and improves the isolation management level of the fire protection system in nuclear power plants.