Abstract: Objective To observe the changes of immune function in sub-health state rat model induced by restraint stress and to explore the mechanism of the traditional Chinese medicine alters the stress . Methods Forty Male SD rats were randomly divided into 4 groups: normal control group，model control group, anti-ageing tablets group and Liuwei Dihuang pills group. To simulate human physiological stress, the sub-health state rat model was induced by restraint . The rats in administration group were given anti-aging tablets and Liuwei Dihuang pills respectively during the model establishment process. At the end of experiment, the indexes of immune function of sub-health state rats tested.Results Twenty-one days afler the experiment, T lymphocyte proliferation capacity, NK cell activity,content of serum IL-2, IFN-γ and thymus index decreased significantly (P<0.05). After treatment of anti-aging tablets and Liuwei Dihuang pills，T and B lymphocyte proliferation capacity，thymus index and content of serum IL-2 were significantly increased (P<0.05), NK cell activity had an increasing trend.Conclusion The immune function decreased in sub-health state rat model induced by restraint stress，and anti-ageing tablets and Liuwei Dihuang pills could improve the immune function of sub-health state rats significantly.The result suggested that the effect of improving immune function by traditional Chinese medicine may be related to regulate cellular and humoral immunity.

Key words: Restraint stress, Sub-health state rats, Immune function;Traditional Chinese medicine (TCM)