This paper investigates the temperature characteristics of the refrigerator with functional duct unit filled in a PCM(Phase Change Materials). Although the EPS(Expended Polystyrene) Duct was used in the existing refrigerator, to improve the temperature distribution of the refrigerator, a functional duct unit with PCM was developed and performance tests were conducted. First, in order to analyse the characteristics of PCM, it tested 100ml of water and PCM in the pyrex tube to proceed with the experimental set-up. Second, the experimental equipment was tested using top mounted freezer type 200~300L volume general refrigerator with EPS duct and the same type refrigerator with functional duct unit filled in a PCM. The temperature standard deviations were lower when installing the functional duct unit when installing the EPS duct. Moreover, when installing the functional duct unit, it protects the temperature rise inside the refrigerator during black out.