Abstract: To prove the Se Lentinan(Se-LEN)'s improve effect to the rat's immunity regulation and T lymphocyte subgroup,we observe the change of the T lymphocyte subgroup and so on through flow cytometer by building a immunodeficiency model with Se LEN's intervention.The results show that the intervene group had obviously improve effect to the proliferation of lymphocyte,CD3+,and CD4+.The spleen index and thymus index increased obviously.The 1/5 dose group's result was lower than control group,and similar to the model group,it promoted the beginning time of lymphocyte's proliferation occurred in one week after intervention.This prove Se LEN can prompt the regulating function of the cellular immunity,can remarkably prompt CD4's proliferation and increase CD4/CD8.The normal dose group is feasible,fast and effective.