2D graphene with high quality holds great promise in improving the performance of the hydrogels owing to its exceptional electronic, thermal, and mechanical properties. However, the structure defects existed in graphene restrict its further applications. Herein, a simple and green method of fabricating defect-free graphene nanosheets with the assistance of supercritical carbon dioxide (SC CO2) is designed. The graphene nanosheets directly assemble with acrylic acid monomer and clay, and a flexible semitransparent hydrogel is fabricated. Benefiting from the excellent properties of the defect-free graphene, the hydrogel exhibits the high mechanical performance, superfast self-healing capability, excellent conductivity, and super photothermal conversion efficiency. According to the advantages above, the graphene/poly(acrylic acid)/clay hydrogels can be used for intelligent sensors for disease diagnosis, artificial electronic skin, and military stealth materials in the near future.