Research on the window operating behavior of offices is of great significance for reducing building energy consumption and improving indoor comfort. The open-plan office is a common office form that involves a large number of people and a complex staff composition. The window operating behaviors in open-plan offices are also random and various. This study took three open-plan offices with different situations (area, office type, staff composition, etc.) as an example, which provides a new perspective on how people behave differently when opening or closing windows. The window operating behaviors in two typical seasons (summer and transition seasons) were recorded and analyzed. The occupants’ schedules and influencing factors of window operating behavior were investigated by questionnaire surveys. In addition, the indoor environmental parameters, occupancy situation, and on-off statuses of windows and air conditioning were acquired through field measurements. Furthermore, the differences in window operating behaviors in the three open-plan offices were compared from the perspectives of influencing factors, duration of the window on-off statuses, and cause of window control actions, among others. In addition, Spearman Correlation Coefficient was used to analyze the ranks of the candidate motivations for window operating behaviors. The preliminary results show that influenced by the personnel composition, type of air conditioner and adjustable degree of windows, the window operating behaviors of different office buildings have larger discrepancies than that in the same building. However, there were some common characteristics in the window regulation behaviors of the three open-plan offices: they were generally influenced by the coupling of environmental factors, schedule factors, and equipment factors. This study reveals that when expand the research object from a single building to multiple buildings, more difficulties and challenges would be involved into behavior research.