To observe the clinical effects of modified Shenqi Decoction in the treatment of chronic fatigue syndrome. Methods:Retrospective analysis of cases were adopted as the design method. A total of 80 patients of chronic fatigue syndrome with deficiency of both qi and yin treated in Department of preventive treatment of diseases, physical examination center and Gao Caida Doctor's Office, Shunyi Hospital, Beijing Hospital of TCM from January 2016 to May 2017 were selected. Oral administration of Shenqi Decoction was given 2 times/ day, 200 mL/ day, and the treatment course was 30 days. According to the curative effect standard to make the follow-up observation and assess the effects. Results:The total effective rates of 4, 6 and 8 weeks taking the decoction were 83%, 88% and 91% respectively. Conclusion:Shenqi Decoction can adjust the qi movement of patients with chronic fatigue syndrome of deficiency of both qi and yin, improve the symptom lacking in strength of chronic fatigue syndrome and improve the quality of life of patients with no adverse reactions.