Air Conditioning System (ACS) is the greatest energy consumer in the buildings. In Summer it consumps ca 50 - 80 percent the energy bill. The study of energy saving for the air-conditioning system is therefore very essential and importent. Not only scientists but also leaders at all levels, particularly in sectors energy management and environment pay special attention to it. The central air-conditioning chiller system of Parliament House designed by the German company GMP-IL uses dry cooler DC (Dry Cooler) to cool the hot water coming out of condenser. According to our calculations, this ACS designed by GMP-IL makes the power consumption increased 153.7 percent compared with the use of traditional cooling towers (TGN). In other words if ACS uses cooling towers, energy saving can reach 1020 kWh per hour full-load operation and can reduce the installed power of the system by 1310 kW.