In order to effectively respond to sudden mountain rainstorm disaster and explore the impact of emergency subjects' psychology on disaster evolution, a method combining game theory and BN was used to simulate the disaster's progression. First, historical disaster cases were analyzed, and consultations with relevant experts were conducted to identify four key scenario elements: emergency scenarios, disaster-forming environment, emergency measures, and human psychology. The Jaccard index was then employed to determine the relationships between these scenarios, while game theory methods were applied to optimize the BN node probabilities, which were initially estimated through case analysis statistics and triangular fuzzy number methods. This led to the construction of a BN-based disaster simulation model that incorporated the psychological factors of emergency subjects in the context of sudden mountain rainstorm disaster. Finally, the model was applied to analyze the "8·21" mountain flood and debris flow disaster in Jinyang, Sichuan, and comparative experiments were carried out. The results demonstrate that the disaster reasoning model is feasible and superior, and the neglect of psychological factors leads to an underestimation of disaster risks. Therefore, emergency management agencies should consider the influence of human psychology on early warnings, evacuation, and resource allocation when designing emergency strategies, in order to improve the effectiveness and adaptability of their measures.