Abstract： Objective To study the therapy effect of boris-Bacillus Calmette-Guérin (BCG) fog-inha-lation on allergic asthma in mice and the relation with IFN-γ, levels in BALF. Methods 40 Kunming mices were randomly divided into three groups: normal group, asthmatic model group, preventive group. The preventive group was randomly divided three groups again :presensitization BCG preventive group,challenging BCG preven-tive group and dexamethasone preventive group. The preventive group after deal, asthmatic model group were made in allergic asthma model in OVA. Pathological scores, bronchoalveolar lavage(BAL) total cell count anddifferentiation were studied. IFN-γ,levels in BAL fluid (BALF) were detected by ELISA. Results The number of BALF total cell count and eosinophils in asthmatic model group were more than in the normal group (P <0.01),IFN-γ level in BALF was decreased(P<0.01);In presensitization BCG prevention group and dexam-ethasone prevention group the number of BALF total cell count and eosinophils were significantly lower than asthma group, and the IFN-γ level significantly higer than asthma group (P<0.01-0.05). These parameters in challenging BCG prevention group were not significantly changing compared with asthmatic model group (P>0.05). Conclusion BCG fog-inhalation can not only markedly inhibit but also treat the airway inflammation in asthmatic mice.