By using ALOHA software as the research tool, and typical toxic and harmful chemical liquid chlorine as research object, the influences of different meteorological parameters ( atmospheric stability customs, emperature and humidity )on the diffusion of liquid chlorine were simulated and screened. Under the simulation condition, wind speed and atmospheric stability were the main influence factors, temperature took the second place, and the influence of humidity could be neglected. When data are lacking, the worst-case simulation factors that would provide reference for environmental risk assessment of toxic and harmful chemicals are as follows： wind speed is 1.5 m / s, temperature is the maximum temperature of the day, atmospheric stability in daytime and night are D and F respectively.