Abstract: Firstly, this review introduced the research background and application status of bio-based hydrogels. According to the different crosslinking mechanisms, physical and chemical hydrogels were classified and described. Then, the hydrogels prepared from cellulose, chitosan, protein and other bio-based materials were summarized based on the classification of the used biomass, including the solvents system of cellulose, the preparation of cellulose-based hydrogels and modification of cellulose derivatization. Also, the feedstock sources and modification methods of chitosan-based hydrogels, as well as cross-linking mechanisms such as electrostatic interaction and imine bond formed by amine groups on their molecular chains were assembled. Protein-based hydrogels with good biocompatibility and bioactivity, formed by β-folded self-assembly of polypeptide chains were depicted as well in this review. Similarly, bio-based hydrogels prepared by using physical or chemical crosslinking of hydrophilic natural polymers such as starch, sodium alginate and carrageenan, were introduced respectively. At the same time, the main applications of functionalized bio-based hydrogels in the biomedical fields were described in detail, including drug sustained release, targeted delivery, cell media, tissue repair scaffolds, wound dressings, etc. In addition, the application and research progress of bio-based hydrogels as adsorbent materials in environmental field were reviewed, and their applications in packaging, sensing, photoelectric catalysis and other fields were also highlighted. Finally, the development opportunities and challenges of bio-based hydrogels were summarized, and the future research directions were prospected.