Objective To observe and explore the effect of activating the spleen for the immune function of spleen deficiency rat.Methods The priscription of Yunpi is composed of Huangqi,Danggui,Cangzhu,Longgu and so on.Reserpine was used to duplicate spleen deficiency model.We divided the rats into three groups:normal grouop,model group and therapy group to observe the effect of activating the spleen for the tissue structure of main immune organ such as spleen and thymus,serum IgG,IgA,IgM,SOD.Results Activating the spleen could significant repair the tissue structure of thymus and improve Ig,SOD.Conclusion Activating the spleen could significant improve immune function of spleen deficiency rat by improving SOD,Ig and repairing the tissue structure of thymus.