Bacillus Calmette-Guérin and other mycobacterial vaccines are important therapeutic methods in a series of chronic inflammatory disorders characterized by Th1/Th2 imbalance in which Th2 type cells and cytokines often increase. However, few studies have investigated whether it can reduce or prevent the symptoms and attacks in children with asthma. This study evaluated the effect of inactivated Mycobacterium phlei inhaled by an atomizing device placed on asthmatic children. In this randomized, single-center, Seretide-controlled study, children aged 4-12 years with newly diagnosed, moderate, persistent asthma were treated with either inhaled inactivated M. phlei or inhaled Seretide patch. The efficacy of inhaled inactivated M. phlei was related with the alleviation of asthma symptoms, improvement of lung function and reduction of bronchial hyper-responsiveness and total serum IgE, which was similar with Seretide. These findings may have important clinical value in confirming inhaled inactivated M. phlei as a new therapeutic method in moderately asthmatic children.