Superadsorbent cellulose-graft-acrylic acid (C-g-AA) hydrogels were successfully prepared via free radical polymerization in phosphoric acid solution. Phosphoric acid solution provides a homogeneous reaction system. The C-g-AA hydrogels have a porous network inner structure with cellulose as the backbone. The introduced carboxyl groups enable the C-g-AA hydrogels with good swelling property (swelling ratio 7327%) and excellent MB adsorption capacity (equilibrium adsorption amount 2197 mg g(-1)). The dynamic swelling behaviors of the hydrogels were tested, water intake of hydrogels followed a non-Fickian type diffusion. The effects of mole ratio of AA to cellulose, the pH of adsorption medium and the initial MB concentration on dye adsorption capacity of hydrogels were investigated. The adsorption isotherm and kinetics fit the Langmuir model and the Pseudo-second-order model well, respectively. Desorption was carried out in weak acid solution and 70% MB could be removed, suggesting the C-g-AA hydrogels had the potential for reuse. POLYM. ENG. SCI., 51:2417-2424, 2011. (C) 2011 Society of Plastics Engineers