To study the thermal properties of different mass ratios of MgCl2·6H2O and Mg(NO3)2·6H2O hydrated salt mixtures as phase change materials for thermal insulation packaging. Samples of MgCl2·6H2O and Mg(NO3)2·6H2O mixture were prepared with different mass ratios, and the cooling curves were measured to discover melting points and super cooling degrees by means of temperature logger. Then the hydrated salt mixtures were put into the high and low temperature alternating chamber to observe the thermal durability. The changes of latent heat were measured by DSC. It turned out that the mass ratio of 5∶5 was a potential phase change material for heat storage, with suitable temperature, no super-cooling, relatively big latent heat and stable cyclic performance.