Abstract The growing energy consumption and thermal comfort of an air-conditioned room have attracted increasing public attention. As such, the performance of air-conditioning systems with two air supply modes for a simplified office room was studied by numerical simulation and physical experiment. An experimental investigation was developed in an environmental chamber to validate the simulation model. Numerical investigation was carried out subsequently for an office setting by the validated CFD model. The indoor thermal environment, human thermal comfort and energy utilization efficiency of two air supply modes were analyzed and compared in this study. The results showed that under both air supply modes, thermal stratification occurred in the model room, and the air flow velocity in the occupied zone was low. In addition, the results indicated that under 21 °C supply temperature, the air-conditioning system with bottom-supply mode provided better indoor thermal comfort of the occupied zone, but the energy consumption was higher than the side-supply mode.