Objectives:To evaluate the correlation between mycoplasma pneumonia infection and the severity of asthma as well as asthma control, to help physicians in respiratory department better make treatment strategies.Methods:Since January 2012 to May 2014, we consecutively recruited 149 out-patients diagnosed with asthma in acute or convalescent phase from the department of respiratory medicine of our hospital. The pulmonary function tests, sputum induction examination, measurement of IgM, IgG and IgE in serum, evaluation of asthma control were carried out for all the included patients.Results:In 78 cases with asthma in acute phase, mycoplasma pneumonia infection was confirmed in 38 cases (48.71%), and in 71 cases in stable state, mycoplasma pneumonia infection was confirmed in 22 cases (30.98%). There was significant difference in the rate of mycoplasma pneumonia infection between the two groups (p<0.05). The FEV1% Pred and ACT scores were significantly lower in mycoplasma pneumonia infection cases than those in no mycoplasma pneumonia infection cases (p<0.05), while the eosinophil count and IgE in serum were significantly higher in mycoplasma pneumonia infection cases (p<0.05).Conclusions:Mycoplasma pneumonia infection may play more important role in the occurrence of acute asthma, and it can lead to decreased pulmonary function, difficulty in controlling asthma and more severe airway inflammation.