Phase change material microcapsules are obtained using a PMMA prepolymer and an organic-solvent free synthesis process. A polymer monomer and an initiator are subject to pre-polymerization in a water bath to form Polymethyl methacrylate (PMMA) prepolymer which is then prepared to be a stabilizer aqueous solution. A phase change material is added to the stabilizer aqueous solution and liquefied in advance, and stirred to form an emulsion by a homogenizing mixer. A starting agent, a cross-linking agent and a Polymethyl methacrylate methyl ester prepolymer are added to the emulsion containing the phase-change material. The emulsion is further stirred by the homogenizing mixer for micro-emulsification which then aggregates in water bath. In this way, the process may use organic-solvent free process to pre-polymerize the polymer monomer into a Polymethyl methacrylate prepolymer and carries out encapsulation and polymerization at an oil-water interface to achieve the preparation of phase change material microcapsules.