Abstract: Objective To establish allergic asthma model in BALB/c mice for investigating the expression of 0X40 in asthma. Methods Mice were sensitized by i.p. injection of OVA ,two weeks late mice were challenged with aerosolized OVA,saline was administered to the mice of the control group in a similar manner. Total number of bronchoalveolar lavage cells and the percents of eosinophils、lympho-cytes were counted； Part of the lung tissues were stained by HE and PAS to show if the murine model can reflect the pathological changes of asthma, and the another part of lung tisuuses were stained by immunohistology to evaluate the expression of OX40. Results Total number of cells and the percents of eosinophils lymphocytes in the BALF were increased in the model group than that of the control group，the difference was statistically significant；the expression of OX40 in model group were more manifest than that of the control group. Conclusion The B ALB/c mice were ideal animals to establish the model of allergic asthma, the expression of OX40 was increased in the lung of mice in asthma.