This study investigated the improvement effect of a small portion of surfactant on the supercooling and the phase change temperature of TMA 30 wt% clathrate compound when surfactant is added to the clathrate compound. The experiments are carried out under various conditions; the concentration of additive ranges between 0.08～0.12 wt% and the temperature of heat source ranges between -8 and -6$^{circ}C$. The experimental results show that the phase change temperature with the surfactant of 0.1 wt% is lower by 1$^{circ}C$ than TMA 30 wt% and the supercooling is reduced by 1$0^{circ}C$.