In this study, two components based polyethylene glycol (PEG)/thermosetting solid-solid phase change material composites as novel form stable phase change material (FSPCM) were successfully prepared via free-radical polymerization. One of the components consists of PEG-based polyurethane acrylate prepolymer and extra pristine PEG. Another component is made up of 1,6-hexanediol diacrylate and benzoyl peroxide. The extra pristine PEG with low viscosity at melting state was used as diluents to decline the melting viscosity of PUA and served as phase change functional chains of the FSPCMs, endowing the FSPCM with high latent heats and flexible application ability for thermal energy storage. The chemical structure, crystalline performances, phase change properties and thermal reliability and stability of prepared FSPCMs were investigated by Fourier transform infrared spectroscopy, X-ray diffraction, polarizing optical microscopy, differential scanning calorimetry and thermogravimetry analysis, respectively. The leakage test results show. that the maximum content of PEG in novel FSPCM without any leakage above the melting point of PEG is 85 wt%. The DSC analysis results show that the novel FSPCMs have high latent heats and the latent heats efficiency of novel FSPCMs is significantly higher than that of the traditional FSPCMs. The prepared FSPCMs exhibit good thermal reliability and stability from the thermal cycling test and TG analysis.