In order to evaluate the air conditioning system performance in terms of control, comfort and energy conservation, this paper presents an approach to modeling automatic control process in a typical conditioned space of an office building. As air- conditioning system, constant volume single-duct system is adopted for interior zone and FCU system for perimeter zone. As for simulation model, we adopted dynamic calculation model expanded by state transition method [1]. The changes of indoor ambient temperature and relative humidity, the PMVs and the energy consumption are investigated by these simulations. The comparison was made between two cases, one is controlled by temperature only and the other is simultaneously controlled by temperature and humidity.