Through dispersed water in normal atmospheric temperature phase change paraffin stably by microemulsification technique,then selected the used sodium alginate as the microcapsule wall material and selected fenestra method to prepare the power storage microcapsules.The microcapsules were compounded with gypsum to prepare building material.Microscope and particle size analyses show that the microcapsules were spheric and in narrow particle size distribution. The power storage density has notable improvement after mixed the water in the paraffin,and the thermal conductivity decreases when temperature is lower than the solid-liquid transition temperature of the paraffin.Heat storage/release testing indicates that the heat storage/release time of the water containing phase change heat storage building material becomes longer obviously,and the lagging time to response the environment temperature change becomes longer,so it could maintain a constant temperature for a longer time.