Abstract: Objective To investigate the clinical significance of negative expiratory press(NEP) test in the diagnosis and treatment of bronchiolitis in infants. Methods A total of 100 infants with bronchiolitis(observation group) and 50 normal infants undergoing the medical examination(control group) in our hospital from June 2013 to October 2014 were selected and documented.NEP technique was performed by using Use McGrady spirometer,and the expiratory flow limited(EFL) was calculated with NEP tidal flow-volume curves and the same flow-volume curve during quiet.Then the tidal value and EFL value were compared with the national norm of normal children. Results One hundred cases of bronchiolitis according to their condition were divided into three groups,including mild group(40 cases),moderate group(30 cases),and severe group (30 cases).EFL in the mild group was (22.75±10.06)%,in the moderate group was(30.46±10.27)%,and in the severe group was (77.39±10.72)%,while in the control group was (12.73±10.01)%,the difference in EFL was statistical significant (P＜0.01);EFL value rose with the severity of the disease.VT/kg in the mild group was (10.52±2.00)ml/kg,in the moderate group was (8.88±2.52)ml/kg,in the severe group was(10.13±2.71) ml/kg,while in the control group was (9.54±2.11) ml/kg,the difference among the groups was not statistical significant,P＞0.05.RR in the mild group was (30.46±10.27) times/min,in the moderate group was (33.00±9.06) times/min,in the severe group was(37.00±9.06) times/min,and in the control group was (31.46±8.27) times/min,there was no statistical significance among the groups,P＞0.05. Conclusion NEP technique can be used to detect the EFL value in infants with bronchiolitis.EFL is closely related with the condition of disease,and raise with the severity.It's possible to evaluate the disease at early stage through the EFL value,which can be used to support early diagnosis and treatment for infant bronchiolitis.