The aim of this study is to evaluate the optimum sodium hydroxide (NaOH) concentrations (2 to 12 wt%) for extraction of cellulose from agricultural waste -rice straw fiber towards preparation of cellulose-based hydrogel. The increase in weight loss with increasing alkaline concentration, suggested that delignification took place progressively up to 6 wt% NaOH as supported by reduction in color intensity of the fiber and chemical analysis using Fourier transform infrared spectroscopy (FTIR).After extraction, the cellulose was firstly dissolved in N,N'-dimethylacetamide/lithium chloride solution. Then, hydrogel was regenerated via phase inversion in ethanol.Remarkably, the highest swelling, gel fraction, tensile strength, and elongation at break (EB) were also found for hydrogels when regenerated from cellulose treated with 6 wt% NaOH. This study verifies that 6 wt% of NaOH is the optimum concentration for cellulose extraction that enhances the key aspects of good properties of cellulose hydrogels. The uniqueness findings of the study is, the swelling ratio and EB increase although gel fraction and tensile strength also increases which has never been reported. Ultimately, extraction of cellulose from waste to produce hydrogels may have novel impact for solving under-utilized biomass as well as good prospects as biomaterials.