Abstract: Male Wistar rats were used to investigate the change of immunological function in rat models of simulation of space flight and the regulation effects of Daibaijie at SPF level. The rats assigned to five groups randomly: normal control group, tail suspended group, tail suspended group with low dose, tail suspended group with middle dose, and tail suspended group with high dose of Daibaijie extract. After 21 days, lymphocyte proliferation, IL-2, IL-6 and IFN-γ, NFκB and IκBα were compared in ConA challenged splenic lymphocyte. The results show that tail suspension can reduce the proliferation function of lymphocyte, decrease the production of IL-2, IL-6 and IFN-γ, and inhibite the activation of NFκB signal transduction pathway. Daibaijie extract can enhance activation of NFκB signal transduction pathway, and improve lymphocyte proliferation and release of cytokines, which indicates that Daibaijie could regulate cellular immunological function.