The application of cyclodextrin (CD) in drug delivery systems (DDS) is mainly reflected in its unique structure and function. Cyclodextrin is a type of cyclic oligosaccharide composed of D-pyranose glucose units connected by α-1,4-glycosidic bonds. It usually contains 6, 7, and 8 glucose units, which are called α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, respectively. Due to its special cylindrical structure, the inner side of the cavity of cyclodextrin is hydrophobic and the outer side is hydrophilic. This structure enables cyclodextrin to encapsulate a variety of organic and inorganic small molecules to form inclusion complexes, thereby changing the properties of these molecules, which can effectively improve the solubility, bioavailability, and targeting of drugs.