The work aims to obtain the phase change energy-storage mixed material that can effectively improve supercooling and maintain higher latent heat and stable performance. The mixed materials with different mass ratios of stearic acid/Mg(NO3)2·6H2O and stearic acid/Na2HPO4·12H2O mixtures were respectively prepared. The long-term cycling performance was tested with low temperature alternating box and its step cooling curve was tested with temperature logger to obtain the phase change temperature and supercooling degree. Then, the reference temperature curve method was adopted to test and compare the latent heat of phase change before and after the cycling of phase-change material. The supercooling degree of stearic acid/Na2HPO4·12H2O mixed material reduced to around 3 ℃. After melting/ solidification cycling for 300 times, the supercooling degree remained constant and the attenuation rate of latent heat was within 20%. Both phase-change mixed materials with similar structures can improve the supercooling degree of inorganic hydrous salt. Stearic acid and Mg(NO3)2·6H2O are of poor compatibility, the latent heat of phase change attenuates dramatically and the cycling stability becomes worse. However, stearic acid and Na2HPO4·12H2O are of good compatibility and with stable performance, which is a good material for energy storage.