In this study, a cold aisle containment system was proposed among various strategies to reduce the energy waste by recirculation air from the hot aisle. To verify the effectiveness of the cold aisle containment system, a test bed which is similar to an actually existing server room was set up in the Internet Data Center(IDC) building. Comparative experiments, conventional open type cooling system and cold aisle containment system were carried out under actual conditions. The result revealed that the range of inlet temperature of the server system was $20{sim}25^{circ}C$ in an existing cooling system and the range of inlet temperature dropped below $20^{circ}C$ by the cold aisle containment system. After all, cold aisle containment system was proved to be the solution for energy saving cooling system.