Modified steel slag-based phase change powders with modified steel slag shell and paraffin core were synthesized by vacuum adsorption. The pore structure, material composition, phase change temperature and phase change enthalpy, particle size distribution, surface morphology of modified steel slag-based phase change powder were characterized. And concrete of modified steel slag-based phase change powders with modified steel slag-based phase change powders were synthesized, the flow performance, cohesive performance and water resistance, mechanical properties, hydration heat performance were analyzing. The results showed that phosphate amount, paraffin amount and pressure in drying oven had great effects on the paraffin intake of modified powders. When phosphate amount 6%(?), paraffin amount 30%(?) and pressure in drying oven 0.04 MPa, modified steel slag-based phase change powder had good phase change energy storage performances, such as phase change temperature 53.7℃ and phase change enthalpy 12.20 J/g. Concrete of modified steel slag-based phase change powders not only had good flow performance, cohesive performance and water resistance, as well as mechanical properties of high early strength and post strength stability, but also had the characteristics of reduce the concrete temperature peak and hysteresis temperature peak to peak.