The invention discloses a method for estimating the source term of conventional explosion radioactive aerosol diffusion, comprising the following steps: aiming at the conventional explosion of radioactive substances on the ground, estimating the explosion equivalent, and estimating the size of the explosion smoke cloud based on the explosion equivalent, and the size of the explosion smoke cloud includes: The height of the explosion smoke cloud, the radius of the explosion smoke cloud, the volume of the explosion smoke cloud, and the density of the explosion smoke cloud, estimate the proportion of the explosion aerosol and the particle size distribution of the aerosol, estimate the impact of the heavy gas effect on the source term, and set the explosion event Nuclides of concern. This method is based on the explosion equivalent, explosive mass, and local wind speed, and comprehensively considers the size of the explosion smoke cloud, the proportion of the explosion aerosol, the particle size distribution of the aerosol, and the influence of the heavy gas effect on the source item to form a source item estimation method. , which is more in line with the actual situation, and the effect is better than that of the point source diffusion model.