Objective：To discuss the effect of modified Shegan Mahuang Chonglou tang on Th1/Th2 cytokines in serumof senile patients with allergic asthm a attack in w inter.Methods：Selected 74 cases of senile patients with allergic asthm a who had positive results of skin prick test of dustmites，and divided theminto two groups randomly，37 cases in each group.Both groups were given the routine treatment with aminophylline and terbutaline，and the control group received the sublingual administration of derm atophagoides farinae drops，while the study group additionally received the oral administration of modified Shegan Mahuang Chonglou tang.Detected Th1/Th2 cytokines in serum，specific SIgG4 and eosinophil cationic protein(ECP)before and after treatment，evaluated the pulmonary functions and scores of allergic asthm a symptoms during daytime and nighttime，and compared the clinical effect and safety.Results：Comparing with those before treatment，the levels of IL-2 and IFN-γ in both groups were increased( P ＜0.05)，and the levels of IL-4 and IgE were decreased( P ＜0.05).Comparing with those in the control group after treatment，the levels of IL-2 and IFN-γ in the study group were higher( P ＜0.05)，and the levels of IL-4 and IgE were lower( P ＜0.05).Comparing with those before treatment，the levels of SIgG4 in derm atophagoides pteronyssinus and derm atophagoides farinae in serumof both groups were significantly increased( P ＜0.05)，and the levels of ECP were significantly decreased( P ＜0.05).Comparing with those in the controlgroup after treatment，the levels of SIgG4 in dermatophagoides pteronyssinus and dermatophagoides farinae in serumof the study group were significantly higher( P ＜0.05)，and the level of ECP was significantly lower( P ＜0.05).After treatment，the pulmonary function indexes including peakexpiratory flow(PEF)，forced expiratory volume in one second(FEV 1 )and FEV 1 /FVC in both groups were increased( P ＜0.01)；comparing with those in the controlgroup after treatment，PEF，FEV 1 and FEV 1 /FVC in the study group were significantly higher( P ＜0.01).Comparing with those before treatment，scores of allergic asthm a symptoms during daytime and nighttime in both groups were respectively decreased( P ＜0.01)；comparing with those in the control group，scores of allergic asthm a symptoms during daytime and nighttime in the study group were respectively lower( P ＜0.01).The total effective rate was 83.78%in the control group and 91.89%in the study group，difference being significant( P ＜0.05).Conclusion：Modified Shegan Mahuang Chonglou tang has optim aleffect in treating allergic asthm a，and can regulate the balance of Th1/Th2 cytokines in serum.