Accident is undesired to anyone. But the research shows that the main cause of accident is unsafe behavior. The interaction mechanism of accident system was analyzed in the process of gas explosion through typical accidents and the conclusion was that the accident was occurred because unsafe behavior induced the dangerous factor in work environment. In order to further acquaint of it, the situation cognition of workers in the coal mine production process was analyzed with the research of aviation. The cognition of safe information in work process was affected by workload, goal, work habituation and others. As workload increased, goal strengthened, the attention apperceived safe information is weaken and the major change of safe information wasn’t apperceived immediately in work environment, and the accident was happened in conditions of unsafe behavior. Finally, the accident model based on situation cognition was posed and some measures were proposed.