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 13.0~27.0 °C and the air supply temperature range for stratum ventilation is 19.0~24.0 °C. By changing the air supply temperature at different time, the daily average saving rate of mechanical refrigeration capacity of displacement ventilation can reach 2.87% and the daily average saving rate of mechanical refrigeration capacity of stratum ventilation is 5.16% for fresh air treatment. And the indoor temperature of the displacement ventilation is more comfortable. Comparing with the cases of reference temperature, the air supply volume under the two ventilation modes both decrease greatly, and the air supply saving rate is up to 22.65% and32.14%, respectively. The indoor pollutant concentration in both ventilation modes is below 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.