Abstract: Objective To study the correlation between the imbalance of effector T cells (Th) and regulatory T cells (Treg) and the severity of bronchial asthma in children and its predictive value for disease control. Methods One hundred and twenty-four children with bronchial asthma from July 2017 to July 2018 were divided into mild group (56 cases) and severe group (68 cases) according to the severity of the disease. Th and Treg levels were detected by flow cytometry, and the correlation between Th, Treg and their ratio and the severity of the disease was analyzed. The children were followed up two months to observe the recurrence of the two groups. The children were divided into recurrence group (45 cases) and non-recurrence group (79 cases), Th and Treg levels were measured and ROC curves were drawn to predict the recurrence of the two groups. Results Th and Th/Treg in severe group were significantly higher than those in mild group, while Treg was significantly lower than that in mild group (P<0.05). Pearson correlation analysis showed that the severity of bronchial asthma was highly correlated with Th, Treg and their ratios (r=0.651, -0.681, 0.786); Th, Treg and their ratios in recurrent group were significantly higher than those in mild group (P<0.05). ROC curves showed that Th, Treg and their ratios had a high predictive power for the recent recurrence of bronchial asthma in children, AUC were 0.511, 0.617 and 0.773 respectively, and the AUC value of Th/Treg was significantly higher than that of Th and Treg (P<0.05). The sensitivity of Th/Treg was 82.22%, significantly higher than those of Th and Treg. Conclusion There is a significant correlation between the imbalance of effector T cells and regulatory T cells and the severity of bronchial asthma in children, and the ratio of Th to Treg has a higher diagnostic efficiency in predicting the short-term recurrence in children.