Sodium alginate has attracted wide attentions due to its wide source, low price, large amount of carboxyl group and hydroxyl group in molecule. In relatively mild environment, sodium alginate can quickly form a three-dimensional network structure of hydrogels. However, the single sodium alginate hydrogel has poor mechanical properties and mechanical strength, and sodium alginate composite hydrogels formed with other substances have been widely used in the field of slow and controlled release of sensitive drugs due to its excellent biocompatibility, biodegradability and pH sensitivity. This paper mainly introduced the preparation methods and properties of sodium alginate composite hydrogels, as well as the application progress in the field of slow release of essential oil in traditional Chinese medicine, and pointed out the existing problems and future research directions of sodium alginate composite hydrogels in the field of slow release of essential oil in traditional Chinese medicine.