Inexhaustible solar energy is the cheapest and most environmentally friendly energy.Therefore, the conversion, storage and application of solar energy are widely concerned. Polyethylene glycol (PEG)/graphene oxide aerogel (GA) composite phase change materials (PCMs) were prepared by introducing PEG into GAs with different oxidation degree via vacuum impregnation. The structures of GAs were tuned by the oxidation levels of graphene oxide (GO). A series of characterizations were used to analyze the chemical structure of GOs, including X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analysis. Structural analyses confirmed that the oxygenated functional groups increased and the hydroxyl groups were transformed into carboxyl and epoxy groups with increasing oxidation level. Morphology analysis showed that the breakage of graphene sheet became more serious with the increase of oxidation level. When GAs prepared by GOs with higher oxidation levels were used, the obtained composite PCMs showed excellent shape-stability during phase change and excellent thermal repeatability. The change of dimension for PGA6-40 heated from 35 °C to 150 °C was negligible under the load of a constant force (7N). This is mainly attributed to capillary force of the porosity and hydrogen bond between PEG and oxygenated functional groups of GO. In addition, an efficient photo-to-thermal energy conversion and storage was realized for the composite PCMs.