BCG and other mycobacterial infections suppress airway hyper-responsiveness and inflammation in asthma models; however, its efficacy in human populations remains controversial. We use inactivated Mycobacterium phlei by way of atomizing inhalation to investigate whether it would protect against asthma in adult patients. Patients with newly diagnosed, uncontrolled, moderate persistent bronchial asthma were randomly divided into two groups. The patients in group A were treated with a solution of inhaled inactivated-M. phlei. Group B were treated with salmeterol xinafoate and fluticasone propionate powder. The Spirometry and Bronchial Provocation Test and Asthma Control Test were carried out; the peak expiratory flow and forced expiratory volume in 1 s-PD20 of the patients in the two groups increased significantly. However, overall, there was no significant difference between the two groups. Asthma Control Test scores of the patients in the two groups were significantly increased. We concluded that inhaled inactivated M. phlei, to a certain extent, improves asthma symptoms, reduces the need for rescue medication and reduces acute exacerbation of asthma. It plays the same role as inhaled Seretide treatment in reducing airway hyper-responsiveness.