Abstract: In order to obtain suitable phase change materials and phase transition temperature in the file of construction, lauric acid (LA)and palmitic acid (PA) were blended to prepare binary eutectic fatty acids (LA-PA) as energy storage material, bio-based SiO₂ (b-SiO₂)powder extracted from waste straw and straw ash was the carrier. Then LA-PA/b-SiO₂ amorphous phase change energy storage materials were prepared by melt impregnation method. The structure and properties of LA-PA/b-SiO₂ phase change composites were analyzed by FTIR, XRD, specific surface area analysis, SEM, DSC and TGA. The results show that there is not a simple physical interaction between the LA-PA and the b-SiO₂. LA-PA is bound to the b-SiO₂ porous network, thus the phase change materials will not leak when the solid phase is changed into a liquid phase. XRD analysis shows that the crystallinity of the LA-PA/b-SiO₂ phase change composite decreases with the increase of b-SiO₂ content. The DSC and TGA analysis show that the LA-PA/b-SiO₂ phase change composites have good properties of phase transformation and thermal stability. The enthalpy of phase change is between 67.36-146.0 J/g.