Abstract: A large amount of radioactive fission products will be released into the containment after severe accidents in a nuclear power plant. Except for noble gases and a small amount of iodine, these fission products are mainly in the form of aerosols. The fission products aerosols can be removed by natural processes, for instance, gravity settlement, agglomeration, Brownian diffusion, electrophoresis, etc. Due to the particularity of aerosol radioactivity in nuclear power plants, the decay process of radionuclides and the interaction process between decay particles and surrounding air will make aerosol particles charged. The interactions between the same sign charges and different sign charges may affect the transport process of aerosol particles, in particular, affecting the aerosol particle agglomeration process. Charges of same sign make aerosol particles repulsive, while charges of different signs make aerosol particles attractive. Therefore, the charge on the aerosol particles will affect the removal process of the fission product aerosol. However, in the current source term evaluation process for the nuclear power plant, the effect of electric charge on the aerosol transport process has been ignored. Considering that the charge amount and charge distribution of radioactive aerosols are the basis for subsequent experiments to study the effect of charge on aerosol transport, the aerosol charge amount and charge distribution were studied. In this paper, the charging mechanism was researched and introduced, mainly including decay process, ionization process, recombination process and attachment process. The models for charging process including the above four processes were developed, and then the charging balance and ions equilibrium equations were obtained. The method for solving the equilibrium equations was introduced. A program for solving the charge distribution and charge amount was developed by FORTRAN language and the calculation results were verified by the experiment results. Referring the parameters in NUREG/CR-6189 report as the input parameters, the charge amount and charge distribution of the aerosol in the containment under the severe accident condition of a typical nuclear power plant were finally obtained which would provide boundary conditions for experimental studies. According to the calculation results, it can be concluded that the aerosol in the containment is negatively charged as a whole under the accident condition of the nuclear power plant. For the aerosol with a typical particle size of (0.1, 5) μm, the corresponding charge range is (0, -25). The amount of charge is related to the particle size. The larger the particle size, the greater the charge. The amount of aerosol particle charge exhibits a normal distribution.