Abstract: Objective To evaluate the preventive and therapeutic effect of thymosin α1 on lung infections in critical patients with tracheotomy. Methods Forty-two patients were randomly divided into treatment group and control group to receive daily subcutaneous thymosin injection at 11.6 mg and saline of 2 ml for 7 days, respectively. Results Compared with the control group, the infection rate, white blood cell count, C-reactive protein, tumor necrosis factor-alpha and interleukiu-6 were significantly lower in the treatment group. Conclusions Thymosin α1 can be effective for prevention and treatment of lung infections in critical patients with tracheotomy and may improve the patients’ immunity and prognosis.