Abstract: With the gradual increase in the production and consumption of shrimp and crabs, a large amount of their shells are directly treated as garbage, resulting in significant environmental pressure. Shrimp and crab shells are rich in chitin. If extracted and prepared, it can not only help reduce environmental pollution but also improve resource utilization. Due to the limitations of existing preparation technologies, production costs, energy conservation and environmental protection, the current utilization of discarded shrimp and crab shells for chitin production remains at a small to medium scale. Therefore, researchers strive to develop new preparation methods and optimizing processes, hoping to expand the production scale of chitin from shrimp and crab shells and improve the efficiency of waste resource utilization. This review mainly elaborates on the research status of preparing chitin from shrimp and crab shell waste using chemical, biological, and physical methods. It also analyzes the advantages, disadvantages, existing problems, and development prospects of various preparation methods, as well as the applications of chitin in bacteriostatic agents, adsorbents, and biofilms. Currently, the traditional acid-base method is mainly used in industry for chitin preparation, with advantages such as mature technology, simple process flow, and convenient operation. However, this method uses strong acids and bases, posing the problem of secondary environmental pollution. In contrast, eutectic solvent method, enzymatic hydrolysis, and microbial fermentation are more environmentally beneficial. Therefore, developing low-cost natural eutectic solvents, constructing recombinant enzymes, and constructing functional microbial communities are the research focuses for preparing chitin from shrimp and crab shell waste in the future.