Based on the major hazard quantitative risk assessment software CASSTQRA V2.0, liquid ammonia storage tank of Shuangyang Foods Co., Limited in Chongqing is taken as the project case by this paper, liquid ammonia leakage accident result is calculated by simulation, and the risk and acceptability on the surrounding environment is quantitatively analyzed. Research results provide not only guidance and basis for safety management of the company and safety supervision of the relevant administrative departments, but also reference for management and operation of other liquid ammonia tank.