The significant reason for the delay in Required Safety Egress Time is the pre-evacuation behavior under building fire. The different behaviors after occupant received fire alarm or cues are influenced by numerous factors. Firstly, there are fifteen pre-evacuation influencing factors which are identified based on literature review and survey, including health status, social influence, affiliation, etc. The influencing factors on pre-evacuation behavior are further analyzed and explained. Secondly, the Interpretive Structural Modeling (ISM) is established and calculated. Then, the adjacent matrix and reachability matrix are acquired. Finally, a hierarchical structure of influencing factors bases on ISM is obtained. The results show that the structural model which presents the influencing factors of pre-evacuation behavior is a five levels hierarchical structure. The direct influencing factors include: actions at recognition & response stage, social influence, etc. The deep influencing factors which are also called origin factors include: age and gender. Therefore, the results indicate that root factors include age, gender and education level. These factors should be paid more attention in order to decrease the delay in the pre-evacuation time. Different evacuation measures should be seriously taken at different places with different crowds in order to increase the success rate of occupant evacuation.
