This paper adopts the analysis method of fire simulation, closely combined with the actual situation of nuclear power plants. On the basis of fully collection of nuclear power plant design data, the designers recorded the layout of ventilation system, ceiling, ignition source and fire compartment boundary in the actual main control room through on-site visits. The main control room fire model is established by using the fire simulation method and fire modeling software CFAST. The curves of hot gas layer height, hot gas layer temperature, thermal radiation and visibility with time in the main control room were obtained. The influence of fire on the habitability conditions in the main control room is evaluated. Combined with the damage time of the equipment, the evacuation time in the case of fire in the main control room is finally summarized and analyzed. This universal analysis method can more truly reflect the fire risk of the main control room and obtain more accurate analysis results, which can be used to calculate the unextinguished probability of fire probability safety assessment.