Chitosan is a kind of natural polysaccharide biomass with the second highest content in nature after cellulose, which has good biological properties such as biocompatibility, biodegradability, hemostasis, mucosal adsorption, non-toxicity, and antibacterial properties. Therefore, hydrogels prepared from chitosan have the advantages of good hydrophilicity, unique three-dimensional network structure, and good biocompatibility, so they have received extensive attention and research in environmental testing, adsorption, medical materials, and catalytic supports. Compared with traditional polymer hydrogels, biomass chitosan-based hydrogels have advantages such as low toxicity, excellent biocompatibility, outstanding processability, and low cost. This paper reviews the preparation of various chitosan-based hydrogels using chitosan as raw material and their applications in the fields of medical materials, environmental detection, catalytic carriers, and adsorption. Some views and prospects are put forward for the future research and development of chitosan-based hydrogels, and it is believed that chitosan-based hydrogels will be able to obtain more valuable applications.