Objective To research the application of oral ambroxol in improving positive rate of sputum smear laboratory testing of Tuberculosis.Methods After immediate microscopic phlegm examination on 1 536 tuberculosis outpatients,them were divided into two groups alternatively and randomly.The referential group took oral placebo while the test group took oral ambroxol.Recheck would be conducted onmorning phlegm after three days,then comprated the positive rate of each group.Results The positive rates of immediate microscopic phlegm examination of the referential and test groups were 4.82％ and 4.56％ (x2 =0.058,P＞0.05) respectively.For the referential group,the positive rates before and after taking medicine were 4.82％ and 5.60％ respectively (x2 =0.475,P＞0.05).The differences had no statistic meaning.The positive rates of morning microscopic phlegm examination after taking medicine of the referential and test groups were 5.60％ and 8.59 ％ ()x2 =5.224,P＜0.05) respectively.The positive rates of the test group before and after taking medicine were 4.56 ％ and 8.59％ respectively (x2 =10.18,P＜0.05).It could be deemed that the difference had statistic meaning.Conclusion O-ral ambroxol can help raise the positive rate of microscopic phlegm examination of the patient with suspected tuberculosis.