When pathogenic microorganisms’ aerosol leakage accident occurred in High-level biosafety laboratories, pathogenic microorganisms’ aerosols into the atmosphere will occur biological decay, and then reduce infectious aerosol concentration in the environment. Based on aerosol leakage environmental risk prediction model, this paper adds half-life decay index in the diffusion model to analyze environmental risks impact of infectious aerosol leakage by pathogenic microorganisms decay. The results show that when microorganism half-life greater than 30min, the less effect to maximum concentration and protection distance of external aerosol by microorganisms half-life. Smaller wind speed, greater impact. When microorganisms half-life less than 10min, concentration and protection distance of environmental aerosol will significantly be reduced. For example, when aerosol leakage in 5m height near the ground, and half-life reduced to 1min, the high-risk area will reduce from 500m to 200m, while the low-risk area from 1500m down to 400m. For aerosol leakage in 25m height, and half-life reduced to 1min, the low-risk area from 1200m down to 0m.