Nowadays, due to limited energy reserves that are available, saving energy in appropriated form is becoming a challengeable subject. One of the new and efficient ways in the field of thermal energy storage (TES) is using of phase change materials (PCM). This paper was examined the effects of two variables including weight percentage of Borax (Borax wt%), and Super Absorbent Polymer (SAP wt%) on the properties of salt hydrates based on Na2SO4.10H2O as PCM. Each variable had five different levels. Response surface methodology (RSM) was used for statistical design and analysis of experiments and process modeling. 2FI and Quadratic models were used for prediction of supercooling and phase segregation, respectively. Among the variables, weight percentage of Borax had a significant effect on supercooling, while the weight percentage of SAP affected phase segregation. In the process of optimization, minimum of supercooling and elimination of phase segregation were predicted at Borax wt% of 10% and SAP wt% of 4.16%.