〔Abstract〕 Objective To investigate the clinical effect of Fuzheng Xiaoliu Decoction in the treatment of cancer causing fatigue (CRF) caused by radiotherapy and chemotherapy for breast cancer. Methods From September 2019 to September 2020, 96 patients with breast cancer CRF in Shenzhen second people's hospital were divided into two groups according to the random number table method, with 48 cases in each group. The control group was given western medicine symptomatic treatment, including application support, correction of anemia, correction of leucopenia, anti infection and pain relief. The control group was given Chinese medicine of Fu Zheng Xiao Liu decoction orally based on the data of the treatment group. The scores of piper Fatigue Scale (PFS), European organization for research and treatment of cancer quality of life questionnaire (EORTC QLQ-C30) of the two groups before and after treatment were compared, Serum levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), C-reactive protein (CRP), natural killer (NK) cells, CD3+ , CD4+ , CD8+ content, and value of CD4+ / CD8+ were compared before and after treatment. Results Before treatment, the PFS scores of the two groups were not statistically different (P > 0.05). After treatment, the PFS scores of the two groups of patients decreased to varying degrees, and the decrease in the observation group was greater than that of the control group, the difference was statistically signifi cant (P < 0.01); the comparison of the scores of the EORTC QLQ–C30 scale between the two groups before treatment, The difference was not statistically signifi cant (P > 0.05). After treatment, the scores of the two groups of patients on the EORTC QLQ–C30 scale increased to varying degrees, and the increase in the observation group was greater than that of the control group, the difference was statistically signifi cant (P < 0.01); the levels of various inflammatory factors in the two groups before treatment In comparison, the difference was not statistically signifi cant (P > 0.05). After treatment, the infl ammatory factors of the two groups of patients were reduced to varying degrees, and the decrease in the observation group was greater than that of the control group, the difference was statistically signifi cant (P < 0.01); the comparison of NK cells and T lymphocyte subsets in the two groups before treatment, The difference was not statistically signifi cant (P > 0.05). After treatment, the NK, CD3+ , CD4+ , CD4+ /CD8+ values of the two groups of patients increased to different degrees, and CD8+ decreased to different degrees. The NK, CD3+ , CD4+ , CD4+ /CD8+ values of the observation group were higher than those of the control group, and CD8+ was lower than the control Group, the difference was statistically signifi cant (P < 0.01). Conclusion Fuzheng Xiaoliu Decoction can relieve the infl ammatory reaction system, enhance the immune function, improve the fatigue state and quality of life. It has a signifi cant effect on the treatment of CRF caused by radiotherapy and chemotherapy of breast cancer.