Polyethylene glycol/silicon dioxide shape-stabilized phase change materials (PEG/SiO2 ss-PCMs) with various molecular weights of PEGwere prepared by temperature-assisted sol gel method, in which PEG served as the latent heat storage material and SiO2 acted as the matrix material. The influences of the molecular weight of PEG on the thermal properties of ss-PCMs were evaluated by synthesized thermal analyzer (DSC/TG), Fourier transformation infrared spectroscope (FT-IR) and transmission polarization microscope. The results show that the simple physical absorption is found between PEG and SiO2 which does not affect phase change behavior of PEG, and PEG still keeps good crystallization characteristics. Phase change enthalpy of ss-PCMs varies from 85.3 J/g to 108.1 J/g under several thermal cycles and raise with increase of PEG molecular weights as well as phase change temperature.