Abstract：Objective：To observe the curative effect of Siwei Xiaoliu tang combined with radiotherapy for malignant brain metastases. Methods：A total of 90 cases of patients with malignant brain metastases were selected and divided into the observation group and the control group according to the random number table method，with 45 cases in each group. The control group was given radiotherapy，and the observation group was additionally given Siwei Xiaoliu tang based on the treatment of the control group. Both groups were treated for four courses， with one week being a course. The changes in indexes of T lymphocyte subsets and Karnofsky(KPS) scores before and after treatment in the two groups were compared； the incidence of adverse reactions during treatment， the clinical effects and the total improvement rate of quality of life in the two groups were observed. Results：After treatment，the values of CD3+，CD4+ and CD4 +/CD8 + in the two groups were increased when compared with those before treatment， and CD8 + indexes were decreased， differences being significant(P＜0.05). After treatment， the values of CD3 + ， CD4 + and CD4 +/CD8 + in the observation group were higher than those in the control group， differences being significant(P＜0.05)；CD8 + index in the observation group was lower than that in the control group， there being no significant difference(P＞0.05). After treatment， KPS scores in the two groups were increased when compared with those before treatment，and KPS score in the observation group was higher than that in the control group，differences being significant(P＜0.05). The total improvement rate of quality of life was 95.56% in the observation group and 82.22% in the control group， the difference being significant(P＜0.05). After treatment， the total effective rate was 93.33% in the observation group and 77.78% in the control group， the difference being significant(P＜0.05). The incidence of adverse skin reactions was 40.00% and 68.89% respectively in the observation group and the control group， the incidence of diarrhea was 33.33% and 64.44% respectively，the incidence of stomatitis was 46.66% and 73.33% respectively； there was significant difference being found in the comparison of adverse skin reactions and diarrhea of grade I to grade II between the two groups(P＜0.05)； there was no significant difference being found in the comparison of the other indexes between two groups(P＞0.05). Conclusion： The therapy of Siwei Xiaoliu tang combined with radiotherapy for malignant brain metastases has a significant curative effect， which can improve quality of life and immune function， with high medication safety.