Abstract: Based on the black box theory, focused on the personnel retention volume of large- scale commercial multifunctional building, this paper chooses a typical commercial multifunctional building as the research object, investigated the personnel retention volume in the working days for one year, then, using the MATLAB software to fit the relationship between the retention volume and the time. The results showed that the retention volume of the working days showed a linear growth, then stable, rapid growth, and finally decayed quickly. The amount of retention volume essentially equal between Monday to Thursday. On Friday, the amount of the retention volume was basically equal with other working days before 17:30, after which there will be a high phenomenon. The peak value of the personnel retention occurred at about 20:00 during the normal working day. According to the relevant data fitting ,obtain the personnel retention experience formula of the normal working day.

Key words: commercial multifunctional building, emergency management, retention volume, black box theory