Objective To investigate the changes of the levels of interleukin(IL)-17 in bronchoalveolar lavage fluid (BALF) of BALB/c mice infected by mycoplasma pneumonia (MP).Methods Sixtyfour BALB/c mice were randomly divided into two groups,normal group (n =32) and MP infected group (n =32).The BALF and lung tissue of two groups were collected after MP infection on day 3,7,14,21,each time 8.HE staining was used to observe the pathological changes of the lung tissue.IL-17 content in BALF was detected by ELISA.Results The inflammatory changes of the lung tissue was the most obvious at 7 day,and had begun to subside at 14 day,disappeared at 21 day after MP infection.IL-17 levels in BALF were (53.783 ±2.218) pg/ml(3 day),(65.913 ± 10.693) pg/ml(7 day),(59.915 ± 8.085) pg/ml(14 day),(57.043 ± 11.997) pg/ml(21 day) in MP infection group,and (46.220 ± 3.260) pg/ml in normal group.BALF IL-17 content increased significantly in MP infection group compared with normal group(P ＜ 0.05).IL-17 content reached its peak on day 7 after MP infection (P ＜ 0.05).Conclusion MP infection increased the level of IL-17 in the mice of BALF,reaching the peak on day 7.MP infection may be involved in airway inflammation in asthma through the IL-17 pathway.