Objective:To explore the relation of the body mass index(BMI) with asthma and its severity in adults.Methods:A total of 83 patients with asthma and 32 control subjects were studied.We analysed the relation of BMI and asthma,the relation of BMI and severity of asthma in all patients,respectively.Results:BMI was higher in asthma groups than in controls(25.19±4.09 vs 22.58±3.32).The values of BMI was(23.24±4.25) kg/m~2 in mild persistent group,(25.25±3.25) kg/m~2 in moderate persistent group,(27.52±4.74) kg/m~2 in severe persistent group.There were significant differences between asthma patients group and the controls,as well as between the mild, moderate and severe persistent patients.Conclusion:BMI is related to asthma and the severity of asthma.