Objective To explore the effect of mycoplasma pneumonia infection on pulmonary function in children with bronchial asthma,and provide objective basis for clinical treatment and prognosis assessment. Methods The clinical data of asthmatic children who were diagnosed and treated in our hospital from October 2013 to October 2015 were retrospectively analyzed.576 cases who have received pulmonary function test in the acute phase of treatment for one week were divided into two groups:positive group (asthma with mycoplasma pneumoniae infection group,144 cases)and negative group (asthma without mycoplasma pneumoniae infection,432 cases).Then the pulmonary ventilation function check indexes were analyzed by statistical software. Results 1)Comparison between negative group and positive group:about the lung ventilation function of two groups,positive group's forced vital capacity (FVC) was higher than that of negative group,the first second forced expiratory volume/forced vital capacity (FEV1 %) was lower than that of the negative group,and there was no statistically significant difference between them;Besides,first second forced expiratory volume (FEV1),peak expiratory flow (PEF) and maximal expiratory flow (MMEF) 25-75,PEF25,PEF50 in positive group were lower than those in negative group,and there were statistically significant differences (P<0.05),giving priority to MMEF 25-75.2)Comparision within positive group:children in the positive group were divide into the high titer group and the low titer group according to mycoplasma pneumoniae antibody titer.And there was no statistically significant difference between the two groups about the lung ventilation function (P>0.05). Conclusion Mycoplasma pneumoniae infection can reduce pulmonary function in children with asthma,giving priority to increasing the small airway obstructive pathological changes,so it is necessary to pay more attention to asthma children with mycoplasma pneumonia infection.