Temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm) was grafted onto the surface of graphene oxide (GO) via reversible addition-fragmentation chain transfer polymerization initiated by γ-ray radiation. Raman spectroscopy and X-ray photoelectron spectroscopy analyses indicated that GO was reduced synchronously upon the radiation grafting polymerization of NIPAAm in an aqueous solution. A pulse radiolysis study demonstrated that NIPAAm reacted with both hydrated electrons (e_aq^-) and hydroxyl radicals (OH) produced by water radiolysis of which the reaction rate constants were 1.0×10¹⁰ L/(mol?s) and (4.3±0.2)×10⁹ L/(mol?s),respectively. The addition reaction between NIPAAm and OH produces a radical at the unsaturated double bond of NIPAAm,which initiates the free radical polymerization of the monomers. Meanwhile,the reaction between NIPAAm and e_aq^- not only consumes strongly reductive e_aq^- but also produces weakly reductive radical anion intermediates,which decreases the reduction degree of rGO. The residual oxygen-containing groups on the surface of rGO with a low degree of reduction degree,such as carboxyl groups,endowed rGO-g-PNIPAAm with good pH responsiveness. Compared to pristine GO without PNIPAAm grafting,rGO-g-PNIPAAm which prepared with an absorbed dose of 3.6 kGy for radiation grafting polymerization exhibited a 30% higher photothermal conversion efficiency under near-infrared LASER irradiation. This study provides a convenient and controllable method for preparing photothermal conversion materials with pH and temperature dual responsiveness.