Abstract：Objective：To discuss the effect of Shenqi tang on immune functions in rats with chronic fatigue syndrome (CFS) and its mechanism. Methods：A total of 40 healthy male SD rats were randomly divided into the normal group，the model group，the paroxetine group and the Shenqi tang group，10 rats in each group. Except for the normal group，CFS models were established in the other groups. After successful establishment，the model group was not given drugs，the paroxetine group and the Shenqi tang group were respectively treated with the corresponding medicine by gavage. The scores of open field test，the immune organ indexes and the expression levels of immunoglobulin G(IgG) and immunoglobulin A(IgA) in serum in rats were detected. Results：During experiment，there was no significant abnormality in the normal group；in the model group，the adaptability to external was weakened，such as lethargy，dysphoria and irascibility；in the Shenqi tang group and the paroxetine group，the fur shedding state was improved when compared with that before drug administration， with forming stool and normal emotions. Compared with those in the normal group， the times of horizontal motion and vertical motion，thymus indexes，spleen indexes and IgA and IgG in the model group were decreased(P＜0.05)，and the time of staying in center was increased(P＜0.05). Compared with those in the model group，the times of horizontal motion and vertical motion，thymus indexes，spleen indexes and IgA and IgG in the Shenqi tang group and the paroxetine group were increased(P＜0.05)，and the time of staying in center was decreased(P＜0.05). Compared with those in the paroxetine group，the IgG and IgA in the Shenqi tang group were increased (P＜0.05). Conclusion：Shenqi tang can improve immune organ indexes in CFS rats，up-regulate the expressions of IgG and IgA，improve immune levels in rats and treat CFS.