The traditional safety margin state technology has low reliability in the case of continuous failure. By analyzing the influence of branch disconnection on node voltage and line load, the fault status events of safety margin components are screened. Then, according to the method of single circuit breaking, the overload circuit of power operation system is judged. And set the setting value of relaying protection, calculate the safety margin of component disconnection, and complete the intelligent truncation technology design of the safety margin state of power operation system. The n-3 fault state space is truncated, and the experimental results show that the intelligent truncation technology of power operation system safety margin state can effectively improve the reliability of the analysis results