In order to determine optimal salt hydrates matching and adding fraction of Na2HPO4 center dot 12H(2)O, crystal characteristics, latent heat of phase change, supercooling degree, and phase change temperature were studied. According to experimental data, optimal salt hydrates matching and adding fraction of Na2HPO4 center dot 12H2O are determined by adopting multi-objective fuzzy optimization model based on analytic hierarchy process. Aimed at 3% Na2SiO3 center dot 9H(2)O-Na2HPO4 center dot 12H(2)O optimized by the method, thermal cycling performance test is implemented. Test results show the following: the Na2SiO3 center dot 9H(2)O-Na2HPO4 center dot 12H(2)O system has lower supercooling degree than Na2HPO4 center dot 12H(2)O. It forms stable crystal after multiple thermal cycles, the phase separation is eliminated completely, and supercooling degree is 3.6 degrees C. Latent heat of phase change maintains at 164 J/g after 100 thermal cycles. It is a modified intermediate product of salt hydrates with development potential. [GRAPHICS] .