Abstract: 　Objective　To explore the effects of obesity on basic lung function and airway hyperresponsiveness (AHR) in children with mild-to-moderate allergic and non-allergic asthma. Methods　According to the skin prick test (SPT), 230 children with mild-to-moderate asthma were divided into allergic group and non-allergic group. Furthermore, based on different body mass index (BMI) Z score, they were also divided into allergic normal body mass group, allergic overweight group, allergic obese group, nonallergic normal body mass group, nonallergic overweight group and nonallergic obese group. The lung function and bronchial provocation test of each group were detected and compared. Results　There were significant differences in peak expiratory flow (PEF), maximal expiratory flows at the 75% of vital capacity (MEF75), MEF50, MEF25, and maximal midexpiratory flow (MMEF) among different groups of mild-to-moderate asthmatic children, and the levels of all above markers were the lowest in nonallergic obese group, followed by nonallergic overweight group (P<0.05). There was no correlation between the BMI-Z score and the indexes of allergic asthma (P>0.05). The pulmonary function indexes (PEF, MEF75, MEF50, MEF25 and MMEF) of nonallergic asthma children were negatively correlated with BMI-Z score (r=-0.314~-0.273, P all <0.01). There was no significant difference in the incidence rate of different grades of AHR among different groups (P>0.05). After bronchial provocation test, the rates of decrease in PEF, MEF75, MEF25 and MMEF were significantly different among the groups (P<0.05), and the lowest rate was found in the nonallergic obese group. Conclusion　Obesity has a greater impact on lung function in nonallergic asthma children, and mainly affects ventilation function.