Abstract: In order to effectively evaluate the emergency evacuation capacity of multi-exit buildings, the evacuation process is analyzed from the view of the most unfavorable point of each evacuation path. Firstly, established the governing equations of four periods including pre- action time, travel time, delayed time, and walking time, as well as the algorithm for calculating the travel time of people at an unfavorable point, then constructed a mathematical model for group evacuation of a multi- exit building. Taking a subway transfer station in Xi'an as a prototype, the evacuation time is calculated by mathematical model and simulation model respectively.The results show that during the evacuation process, travel time at the most unfavorable point in a evacuation of a certain evacuation structure is not only related to the evacuation capacity of the structure, but also related to other evacuation structure before passing the evacuation structure, and the number of people to be evacuated. The evacuation capacity of the stairs and the speed of people moving on the stairs are positively related to the width of the stairs.It has a negative correlation with the thickness and width of the human body. The calculation time error with the simulation model is only 1.47%.

Key words: multi-exit building, the most unfavorable point, evacuation model, traffic capacity