Fatty acid/SiO_2 composite,a phase change material(PCM),was prepared by sol-gel method.PCM changes phase from solid to liquid inside SiO_2 gel hole,and appearance of composite is always solid.The lightweight PCM wallboard was prepared by bonding PCM composite on expanded polystyrene(EPS) board,so that the shortcoming of low thermal storage capacity of common lightweight wall is overcome.Thermal insulation and temperature control experimentation were conducted by models fabricated of two kinds lightweight wall-materials with or without PCM,the result shows that the thermal-storing capacity of lightweight PCM wall-material could be greatly improved.