Objective To detect the expression of Th17 levels about peripheral blood in patients with bron-chial asthma in bronchoalveolar lavage fluid,and to investigate its effect in pathogenesis of bronchial asthmaand. Methods Patients with acute bronchial asthma from 2014 April to 2014 November were collected in the experiment. There are 52 cases as observation group (group of patients with asthma),and the patients were then divided according the severity (mild,moderate,severe);in addition,select 50 healthy people in the same period in our hospital as con-trol group healthy control group.Collect peripheral blood and bronchoalveolar lavage fluid,the expression of specific transcription factors ROR gamma T and cytokine IL -17 in the peripheral blood and bronchoalveolar lavage fluid in Th17 cells levels were detected by real -time fluorescent quantitative PCR.Results The expression of IL -17,ROR gamma T in peripheral blood and bronchoalveolar lavage fluid of the observation group were higher than the control group;the expression of IL -17,ROR gamma T in alveolar lavage fluid quantity and peripheral blood with severe patients in the observation group were higher than that in the mild patients,differences were statistically significant (P <0.05).Conclusion There are 17 auxiliary T lymphocytes in patients with bronchial asthma in vivo (Th17) advantage of expression,Th17 may play an important role in the pathogenesis of bronchial asthma.Bronchial asthma patients body may have advantage to heip expression of T lymphocytes 17 (Th17).Th17 may play an important role in the pathogenesis of bronchial asthma.