Vitamin A deficiency is a systemic disease caused by a lack of vitamin A in the body, with eye and skin lesions as the main symptoms. The patients are mainly infants and young children, and often coexist with malnutrition, accompanied by protein-energy malnutrition, etc. Vitamin A has many important functions in the body. It plays an important role in the function of the retina, is obviously necessary for the growth and differentiation of epithelial tissue, and is also required for bone growth, reproduction and embryonic development. It also has a stabilizing effect on various cell membranes. It thus regulates the permeability of the membrane. The functions of vitamin A are realized through different molecular forms. Retinaldehyde plays a role in vision. Retinol plays a role in the reproductive process, while retinoic acid or a metabolite is important for other functions.