In recent years, HVAC systems of commercial buildings imposed heavy load on power demand, especially during summertime on-peak periods. The HVAC power consumption of commercial buildings usually accounts for 40% of total which indicated huge potential for energy-savings if proper operation strategies can be implemented. In this research, three different operational strategies were studied in an attempt to conserve energy, namely: the Night Purge, Free Cooling,and Pre-cooling. They were simulated , under the local weather conditions, and then validated with full-scale experiments.The experimental results indicated that significant load-shifting effect can be experienced, which also warranted good engineering application potentials when coupled with other HVAC energy-savings operation strategies.