Abstract: To investigate supplementation of vitamin A and vitamin C on the effects of immunedificiency caused by malnutrition, we used rats as an animal modeli Restricted food intake from th e 35th day to th e 45th day, The result indicated that rats with malnutrition had thymus atrophy1 decease number of plaque~forming cells in spleen lymphocytes and proliferation to Con A or LPS. Supplementation of vitamin A can significantly increase thymus weight, spleen proliferation and antibody production to Con A or LPS. Supplementation of vitamin A can significantly increase thymus weight, spleen proliferation and antibody production, but supplementation of Vitamin C had no this effect. This result proposes that vitamin A can increase immun e fu nction and play an immportan t role in prevention and treatment of infectious deseases.