Objective To study the effect of obesity on pulmonary function in patients with bronchial asthma in non-acute episode. Methods From Jun. 2015 to Feb. 2016, a total of 120 patients with bronchial asthma in non-acute episode in our hospital were taken as the clinical research objects, and they were divided into obesity group(BMI>25kg/m2 )(n=40) and non-obesity group(≤25kg/m2 )(n=60) according to body mass index (BMI). In the past 6 months, the symptoms and drug use in the two groups were observed and compared, pulmonary function indexes including forced vital capacity(FVC), forced vital capacity percentage of predicted value(FVC% pred), forced expiratory volume in 1s (FEV1), forced expiratory volume in 1s percentage of predicted value(FEV 1% pred) and FEV1/FVCin the two groups were detected by pulmonary function instrument. Results In the past 6 months, the asthma and cough time in the obesity group was obviously less than that in the control group(P<0.01), the using dosage of hormone in the obesity group was obviously higher than that in the control group(P<0.01), the FVC% pred, FEV 1% pred and FEV1/FVC in the obesity group were all significantly lower than those in the non-obesity group(P<0.02). Conclusion Compared with non-obese patients, obese patients with bronchial asthma in non-acute episode has the following characteristics: more serious asthma and cough symptoms, more using dosage of drugs and obviously poorer pulmonary function.