To explore the effects of Panax quinquefolium L.under different processed time on hypoimmunity in mice.Methods:Seventy KM mice，randomly divided into a blank control group and positive drug group，model group，2 h processed group，4 h processed group，6 h processed group and crude drug group，were given same amount of normal saline，levomisole (30 mg/kg)，2 h extract (200 mg/kg)，4 h extract (200 mg/kg)，6 h extract (200 mg/kg) and crude drug extract (200 mg/kg) each day，respectively.Except the blank group，the other mice were treated by cyclophosphamide (50 mg/kg) through abdominal administration to induce low immune mice model.To detect the spleen and thymus index，indexes of the clearance rate of carbon，ConA and LPS were applicated to induce spleen lymphocyte proliferation response，testing each value of T lymphocyte subsets in mice.Results:All kinds of processing time of ginseng and crude drugs can influence the levels of spleen and thymus index，expurgation index，index，spleen lymphocyte proliferation reaction and the number of CD4+ and CD8+ cells，and can increase the ratio of CD4+ / CD8+ cells in the lower immune mice.In each processing group，2 h group was more active than the other groups.Conclusion:Different processing time of Panax quinquefolium L.water extract on hypoimmunity in mice varies in effect，in which 2 h processed time has the best activity and is worth of further research.