Abstract： Objective： To observe the curative effect of modified Wuwei Xiaodu Decoction for severe infection with inward invasion of heat toxin syndrome and its effect on inflammatory responses and immune function. Methods：A total of 120 cases of patients with severe infection with inward invasion of heat toxin syndrome were selected and divided into the control group and the observation group according to the random number table method， with 60 cases in each group. The control group was treated with symptomatic treatment and routine anti- infective therapy， and the observation group was additionally treated with modified Wuwei Xiaodu Decoction based on the treatment of the control group. Both groups were treated for two weeks. Before and after treatment， the scores of Acute Physiology and Chronic Health Evaluation Ⅱ (APACHE Ⅱ) and Sequential Organ Failure Assessment (SOFA)， and the levels of CD3 +，CD4 + and CD4 +/CD8 +，C- reactive protein (CRP)，procalcitonin (PCT) and white blood cell (WBC) count in the two groups were observed and compared. Results： Before treatment， there was no significant difference being found in the comparison of scores of APACHE Ⅱ and SOFA between the two groups (P＞0.05). After treatment，the scores of APACHE Ⅱ and SOFA in the two groups were decreased (P＜0.05)，and the scores in the observation group were lower than those in the control group (P＜0.05). Before treatment， there was no significant difference being found in the comparison of levels of CD3 + ， CD4+ and CD4+/CD8+ between the two groups (P＞0.05). After treatment，the levels of CD3+，CD4+ and CD4+/CD8+ in the two groups were increased (P＜0.05)，and the levels in the observation group were higher than those in the control group (P＜0.05). Before treatment，there was no significant difference being found in the comparison of levels of CRP， PCT and WBC between the two groups (P＞0.05). After treatment， levels of CRP， PCT and WBC in the two groups were decreased (P＜0.05)， and the levels in the observation group were lower than those in the control group (P＜0.05). Conclusion： Modified Wuwei Xiaodu Decoction combined with symptomatic treatment and routine anti-infective therapy can effectively improve the immune function of patients with severe infection with inward invasion of heat toxin syndrome，effectively relieve inflammatory responses，and improve curative effect of anti-infection.