A new system with main cooling and pre-cooling systems using a vapor compression cycle and natural circulation, respectively, has been developed to save energy in a mobile telecommunication base station. In such base stations, as more information is transferred, more heat is generated, so the energy consumption for the cooling increases correspondingly. In addition, a field investigation revealed conventional cooling systems are not so effective in terms of energy consumption. According to the calculation results, the newly developed system can reduce annual energy consumption by approximately 50% due to its high performance. At the test site, the new system showed a system COP of 6 with an outdoor temperature of 1°C(34°F) and a pre-cooling capacity of 200W/K(378Btu/h°F), respectively. From the data recorded in an actual base station, it demonstrated the ability to reduce annual energy consumption by approximately 50% as we had expected. The annual average system COP would also exceed 5.0.