Objective To explore the best decocted time by observing the effect of Yinqiao Powder（Lonicerae and Forsythiae Powder） in different decocted time on immunity of rats with immune suppression.Methods The 88 qualified male rats were randomly divided into 11 groups with 8 in each: normal control group

model group

groups of Yinqiao Powder decocted for 3 minutes in high

medium and low concentrations

groups of Yinqiao Powder decocted for 6 minutes in high

medium and low concentrations

and groups of Yinqiao Powder decocted for 12 minutes in high

medium and low concentrations.Except for the normal control group

the rats in all other groups were made immune suppression models by using cyclophosphamide.Yinqiao Powder decoction was given by intragastric administration for 7 days.Then

the carbon clearance ability of reticuloendothelial system

the swimming endurance

the quantity of T cell subpopulation in peripheral blood

and the weights of spleen and thymus of all groups were determined.Results Yinqiao Powder decocted for 3 minutes in high and medium concentrations and decocted for 6 minutes in high concentration could improve remarkably the swimming endurance（P<0.05）

without significant difference among these 3 groups.Except for those decocted for 6 minutes in low concentration and decocted for 12 minutes in medium and low concentrations

the other groups of Yinqiao Powder could improve remarkably the phagocytosis of reticuloendothelial system

and the K and α values were increased remarkably（P<0.05）

of which

the effect of those decocted for 3 minutes in high concentration and decocted for 6 minutes in high concentration was the best.Yinqiao Powder could increase remarkably the quantity of CD4+ T cell of peripheral blood（<0.05）.There was a tendency in Yinqiao Powder groups in increasing CD8+ T cell of peripheral blood

but not remarkably.Yinqiao Powder decocted for 3 minutes in high concentration could increase remarkably the weight of thymus and spleen（P<0.05）.Conclusion Yinqiao Powder is effective in improving immunity in rats with immune suppression and the effect of that decocted for 3 minutes was the best.