Objective To investigate the clinical diagnostic significance of detecting T in peripheral blood lymphocyte subsets (CD4+,CD8+ and the ratio of pulmonary tuberculosis with diabetes) and explore drug therapy of the five thymus peptide combined anti-tuberculosis on the diabetes complicated with pulmonary tuberculosis.Methods Eighty cases of pulmonary tuberculosis complicated with diabetes mellitus were selected as our treatment subject,who were treated with anti-tuberculosis drug treatment and five thymus peptide regulating immunity treatment.T lymphocyte subsets (CD4 +,CD8 + and their ratio) were detected.Meanwhile acid-fast bacilli and image detection were performed.Another 80 cases were as our control group that treated with anti-tuberculosis drug.Results Following the thymus peptide five treatment for 1,2,and 6 months,T lymphocyte subsets were (CD4+:(34.34 ± 7.32) ％,(39.23 ± 6.62) ％,(41.06 ± 7.13) ％),(CD8+:(31.42 ±8.91)％,(32.52 ±8.58)％,(32.12 ±8.59)％),(CD4+/CD8+:(1.23 ±0.31),(1.34 ±0.30),(1.36 ± 0.32),higher than that of before treatment (30.26 ± 8.25) ％,(30.36 ± 9.86) ％,(1.13 ± 0.42) CD4 +.Through 2 months treatment,CD4+,CD4+/CD8+ of patient in treatment groups were different with that of control group (P ＜ 0.01 or P ＜ 0.05).80 patients after anti-TB plus application thymopentin regulating immunity for 2 months,normal sputum negative conversion rate of CD4+ was 97.2％ and improvement rate was 98.0％.However cases with high CD4+ T lymphocyte subsets showed 78.6％ negative rate of acid-fast bacilli and 88.0 ％ cured rate,and there was significant difference (x2 =4.764,7.680,respectively,P ＜ 0.05).Conclusion Thymic peptide five might have the ability of improving the cellular immune function in patients with pulmonary tuberculosis and diabetes.The prognosis is better when T lymphocyte subsets CD4+ of patient was back to normal through treatment.