Abstract: In view of the problem that the current factor analysis method is difficult to determine the impact of new factors on the evolution of accidents during the dynamic process of accident incubating, a dynamic reduction algorithm for causative factors of safety accidents is developed based on the factor space and rough sets theories.Based on the factor static reduction algorithm, by defining the importance of factors on accident evolution, the definition and algorithm of factor importance were proposed and the dynamic reduction algorithm of the factors causing safety accidents is given by ranking the importance of accident-causing factors.Taking coal and gas outburst accident as the research object, an application example of dynamic reduction algorithm for outburst accident causal factor is given.The research shows that the importance of influencing factors of safety accidents is an important measure to whether safety accidents occurs or not.The greater the importance of factor, the stronger the causal logic relationship between it and safety accidents, and the more attention should be paid to in the accident safety prevention and control.The original reduction results can be effectively used by the factor dynamic reduction algorithm through the importance ranking and determination analysis, thus the influence of new factors to accidents evolution can be quickly obtained, and accident causing factors were determined quickly to achieve overall reduction.