Abstract: ob＜x＞jective To investigate the diagnostic value of nasal eosinophil in children with bronchial asthma and its relationship with disease severity. Method 120children with bronchial asthma who were treated in our hospital from June 2017 to December 2018 were selected as observation group. According to the degree of illness, the observation group cases were divided into intermittent group of 53 cases, mild group of 44 cases, moderate group of 12 cases, and severe group of 11 cases. 60 healthy volunteer children were Recruited as a control group. Observation of nasal eosinophil levels between the control group and the observation group. To investigate the diagnostic value of nasal eosinophil in children with bronchial asthma and to compare the diagnostic value of induced eosinophil in peripheral blood and peripheral blood. Analysis of the relationship between nasal eosinophils and C-ACT score, FEV1, serum IgE and exhaled nitric oxide. Results The levels of nasal eosinophil in the subgroups of the observation group were significantly higher than those in the control group, and the levels of nasal eosinophil in the subgroups of the study group were statistically significant (P<0.05). The sensitivity of nasal eosinophil in the diagnosis of childhood bronchial asthma is 80.1%, and the specificity is 81.8%. The diagnostic value of nasal eosinophil is better than that of induced eosinophil and peripheral blood eosinophil. Nasal eosinophil were negatively correlated with C-ACT score and FEV1 value, and positively correlated with serum IgE levels and exhaled nitric oxide. Conclusion The level of nasal eosinophil in children with bronchial asthma is positively correlated with the severity of the disease and can be used as a clinically effective diagnostic indicator. Nasal eosinophil is simple to operate and highly feasible, and are worthy of promotion and application.