A series of fatty acid/poly methyl methacrylate (PMMA) shape-stabilized phase change materials ( PCMs) have been prepared by bulk polymerization method. In the composite, fatty acid (capric acid, stearic acid, and their eutectic mixture) acts as core material and PMMA serves as matrix, which coats the fatty acid to prevent the leakage of melted fatty acid. The prepared shape-stabilized PCMs were characterized on the morphology, phase change behavior, chemical characterization and thermal properties. The results indicate that the composites with proper phase change temperature and latent heat are able to keep solid morphology in macro level during thermal storage process. Thermal cycling test also indicates that the composite PCMs have good thermal reliability. Moreover, thermal conductivity and thermal performance are investigated and the results show that the shape-stabilized PCMs have the higher thermal conductivity than fatty acid and exhibited good thermal performance in controlling the atmosphere temperature.