Ventilation mode has important effect on indoor environmental quality and building operation energy consumption. Based on the unsteady heat transfer method, the thermal boundary conditions of building envelope are obtained. The ventilation effect and energy-saving characteristics of displacement ventilation and stratum ventilation in an office in cold zone are compared when the building envelope thermal properties meet the requirement of 65% energy saving. The results show that under the premise of thermal comfort, the air supply temperature range of displacement ventilation is 13.027.0 ℃ while that of stratum ventilation is 19.024.0 ℃. By changing the air supply temperature at different time, the daily average saving rate of mechanical refrigeration capacity of displacement ventilation and that of stratum ventilation can reach 2.87% and 5.16% respectively for fresh air treatment. And the indoor temperature of the displacement ventilation is more comfortable. The air supply volume under both ventilation modes decreases greatly compared with that corresponding to the basis air supply temperature, and the air supply saving rate is up to 22.65% and 32.14%, respectively. The indoor pollutant concentration under both ventilation modes is below the standard value. The research has important engineering guiding significance for further exploring the correlation between climatic conditions and ventilation modes, optimizing the design and operation management of air-conditioning systems.