Chitin is the second largest natural polysaccharide after cellulose, which is polymerized by N-acetyl-D-glucosamine, having important application value in agriculture, industry, medical treatment and other fields. Natural chitin exists in a highly crystalline state with complex barrier against degradation. Bacteria can secrete multiple chitinases with special functions to degrade chitin efficiently. Chitinases mainly distributed in GH18 and GH19 families in CAZy database. There are obvious phenomena of gene amplification and multi-domain combination of chitinase genes in bacteria. Chitinases with various action modes in different GH families can act synergistically to break the barrier and complete efficient degradation of crystalline chitin. Therefore, in-depth analysis of the structure and function of bacterial chitinase is of great significance for efficient degradation and high-value conversion of chitin. In this paper, the classification and structural characteristics of bacterial chitinase were introduced, which laid a foundation for further research on the functional mechanism of the enzyme. After that, the action mechanism of chitinases belong to GH18 and GH19 families, including the binding mechanism of enzyme to substrate, catalytic mechanism was summarized to further understand the characteristics of chitinase at molecular level. It is worth noting that processibility is an important characteristic of chitinase to efficiently degrade crystalline chitin, so the molecular mechanism of chitinases, including the effects of polar amino acid residues and aromatic residues on processibility was focused on. In addition, the synergistic degradation modes of extracellular chitin degradation enzymes in 3 different bacterial were summarized, which provided a theoretical basis for the design of efficient chitin degradation enzymes. Through a review of the research progress of molecular modification of chitinases, the role of protein engineering design strategy based on structural bioinformatics and big data deep learning in future modification is prospected, which provides a new perspective and ideas for the design and rational modification of chitinase. To sum up, this paper introduces the relative knowledge of chitinase from structure to mechanism and function to application, which provides a comprehensive foundation for further study of chitinase, the structural and molecular basis for the design of high-functional enzyme, and a theoretical basis for the application of chitinase.