Abstract: The radioactive impact of unfiltered air leakage (internal leakage) in the main control room of a nuclear power plant is an important part of habitability evaluation. At present, the dose model for this part is too simplified and does not accord with the actual engineering design. Combined with the actual design characteristics of a nuclear power plant, this study studies the migration mechanism of internal leakage source terms, deduces the differential equation of radioactivity, establishes the habitable internal leakage dose model of the main control room, selects typical design basis loss of coolant accident (LOCA) and large break loss of coolant accident (LB-LOCA) with reactor melting to carry out the application of the model, and compares it with the commonly used simplified model at present. The results show that the dose result of the simplified model under LB-LOCA condition is smaller than that of this model, and the simplified model can not cover all accident scenarios. After analysis, the internal leakage dose model established in this study is more in line with the actual scenario, suitable for the impact evaluation of internal leakage in the habitable area of the main control room, and can be used for the verification of internal leakage test results and engineering project design.