In this study, cellulose-based superabsorbent hydrogel was synthesized from sodium carboxymethyl cellulose (CMC-Na), acrylic acid (AA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to enhance its water absorbency and salt tolerance for soil-conditioning applications in areas suffering from drought and soil salinization. Superabsorbent hydrogels (SHs) were prepared by CMC-Na and AMPS successfully, using chemical graft technology. Structure, morphology, thermal stability, and water absorbency of SHs were deduced. The cellulose-based hydrogel showed a high salt tolerance that the maximum water absorbency reached 604 and 119% in distilled water and saline water, respectively. The swelling behavior in aqueous solvents indicated that the water absorption of hydrogels was improved with the increasing ratio of CMC-Na. All SHs exhibited adsorption of nitrogen with the maximum adsorption of ammonia nitrogen 30 mg·g and the presence of hydrogels could slow down the loss of nutrients in the soil. This study provided a feasible strategy that AMPS was substituted by CMC-Na to synthesize SHs with strong water absorbency and high salt tolerance which could be efficiently applied in agriculture as a soil conditioner.