This systematic review was conducted to assess the curative effect of Thymosin alpha 1 in the acute exacerbation of chronic obstructive pulmonary disease (AECOPD) patients. Six electronic databases including EMBASE, PubMed, Cochrane Library, China National Knowledge Infrastructure Database, Chinese Biomedical Database, and Wanfang Database were searched for eligible papers focusing on the thymosin alpha 1 treatment in AECOPD patients. The effectiveness outcomes included T cell subset, pulmonary function, arterial blood gases, and the length of hospital stay. Stata and Review Manager Software were used for data analysis. Thirty-nine randomised controlled trials with a total of 3,329 patients were included. Compared with the control treatment, Thymosin alpha 1 therapy significantly improved forced expiratory volume in 1 second [MD = 0.29, 95% (0.26, 0.32), p <0.001] and the ratio of forced expiratory volume in the first second to forced vital capacity [MD = 6.24, 95% (3.83, 8.65), p <0.001], increased the arterial partial pressure of oxygen [MD = 7.24, 95% (3.42, 11.07), p = 0.0002], lowered the arterial partial pressure of carbon dioxide [MD = -5.85, 95% (-9.38, -2.33), p = 0.001], shortened the length of hospital stay [MD = -5.39, 95% (-7.82, -2.97), p <0.001], raised the level of CD4+ T lymphocytes count [MD = 7.54, 95%(6.66, 8.41), p <0.001] and the ratio of CD4+/CD8+ [MD = 0.40, 95% (0.34, 0.46), p <0.001], and decreased level of CD8+ T lymphocytes count [MD = -2.74, 95% (-3.86, -1.63), p <0.001]. Thymosin alpha 1 could significantly boost the immune function, and improve pulmonary function and arterial blood gas of AECOPD patients than routine treatment only. More high-quality randomised controlled trials are needed to further confirm Thymosin alpha 1 efficacy. Key Words: Thymosin alpha 1, Efficacy, Acute exacerbation of chronic obstructive pulmonary disease, Meta-analysis.