To address the challenges of high risk and difficulty in quantitative analyzing hazardous chemical storage tank area leakage accidents, a composite method based on STAMP was proposed to elucidate the accident mechanisms. It clarifies the logical relationships among causal factors and quantitatively evaluate the impacts of accident causation, thereby enabling nonlinear quantitative accident analysis. First, the STAMP-24Model was utilized to construct an accident analysis diagram for hazardous chemical storage tank leakage, identifying system components, hierarchical relationships, as well as analyzing accident causal factors and their logical connections. Subsequently, Interpretive Structural Modeling (ISM) method was applied to determine path relationships and hierarchical structures among causal factors. Node importance analysis based on degree and clustering coefficients, as well as BN node analysis, was conducted to assess the criticality of causal factors on system. Finally, the validity and feasibility of the method were verified through a case study. The results show that organizational management failure (e.g., failure to implement safety rules and regulations, lax implementation of engineering management regulations) is the core driver of accident risk evolution, with a total degree value of 53.3%, and a significant coupling effect with physical and personnel layer factors.