Abstract: It is important to evaluate the containment dose rate under severe accident conditions for some aspects of a nuclear power plant, such as severe accident management and emergency response. In this work, the MELCOR code was used to simulate the sequence of severe accidents, calculate masses of radioactive fission products released to containment. The ORIGEN2 code was used to calculate the γ source intensity. The MCNP code was used to calculate the containment dose rate when each group of radioactive fission products was all released to containment. The containment dose rate was finally calculated by a fitting formula. This method was used in the 300 MW units of CNNP Nuclear Power Operations Management Co. Ltd and was proved to be available.