In order to overcome its supercooling and phase separation,Na₂S₂O₃ ·5H₂O ,a kind of phase- changematerial,was modified,with CaSO₄ ·2H₂O,naphthol as the nucleating agents,and with carboxymethyl cellulose(CMC),activated clay and solvable paraffin as the thickening agents. Then,the thermal storage/release perfor-mance of the modified Na₂S₂O₃ ·5H₂O  was investigated by using the cooling curve and the DSC analysis.The re-sults indicate that (1) CaSO₄ ·2H₂O,naphthol and naphthol- NaCl all play important role in the modification of Na₂S₂O₃ ·5H₂O ; (2) as compared with CMC，solvable paraffin and activated clay are of higher thickening effi-ciency for Na₂S₂O₃ ·5H₂O - CaSO₄ ·2H₂O with the same dosage of thickening agent; (3) Na₂S₂O₃ ·5H₂O  modi-fied with CaSO₄ ·2H₂O and activated clay achieves the crystallization and releases thermal energy at above 27℃,with the highest exothermic temperature varying from 43 to 48℃ and with an exothermic duration being more than80min; (4) Na₂S₂O₃ ·5H₂O modified with naphthol- NaCl possesses good stability and is of a phase- change tem-perature varying from 41 to 46℃ at different times of heat storing- releasing circulation,and the heat release evenlasts for more than 70 min; and (5) the phase change enthalpy of modified Na₂S₂O₃ ·5H₂O  varies from 150 to180J/g,while no phase separation occurs in the thermal storage/release process.