Liquid ammonia leakage accidents can cause serious consequences. This paper makes research on the liquid ammonia leakage accidents based on safety system engineering theory model. Shanghai Baoshan”8.31” liquid ammonia leakage accident is used as an example in this paper and the direct and indirect reasons for the accident are analyzed and combined into four factors: human, material , management and environment. The fault tree is drawn, then the minimal cut sets, the minimal radius set and the structural importance degree are calculated to obtain the method to improve the system security. Based on the analysis of the causing factors and the fault trees, this paper establishes the theoretical risk control system model of liquid ammonia leakage accidents. According to the model, the corresponding countermeasures for liquid ammonia leakage accident prevention are put forward, providing the basis to prevent liquid ammonia leakage accidents scientifically, reasonably, and effectively. CLICK HERE for the paper from School of Management Studies, Shanghai University of Engineering Science.