Abstract： Objective:To investigate the clinical efficacy of hyperbaric oxygen (HBO) as adjuvant therapy on children with viral encephalitis (VE), and its effect on the pathway of T helper 17 (Th17) cells / regulatory T (Treg) cells and Notch signaling pathway in lymphocytes.Methods:A total of 78 children with VE treated in the Affiliated Hospital of Southwest Medical University from March 2017 to March 2019 were divided into two groups by the random number table method, with 39 cases in each group. The control group received conventional treatment, and the HBO group was treated with HBO on the basis of the treatment of the control group. The therapeutic effects and scores of Mini-mental State Examination (MMSE) of the two groups were compared. The levels of Th17 cells and Treg cells in peripheral blood and the level of Notch signaling in lymphocytes were analyzed.Results:The total effective rate of the HBO group (94.87%, 37/39) was significantly higher than that of the control group (74.36%, 29/39); the time period to clinical symptom relief, the number of seizures, and the count of lymphocytes in cerebrospinal fluid of the HBO group were significantly lower than those of the control group; and the MMSE score of the HBO group was significantly higher than that of the control group; all the differences above were statistically significant ( P<0.05). After treatment, the levels of Th17 cells and its related factors were significantly decreased, while the levels of Treg cells and its related factors were significantly increased ( P<0.05). After treatment, the ratio of Th17 cells / Treg cells and the levels of Th17-related factors in the HBO group were significantly lower than those in the control group ( P<0.05), while the levels of Treg-related factors in the HBO group were significantly higher than those in the control group ( P<0.05). After treatment, the levels of Notch signaling were significantly decreased in both groups ( P<0.05). After treatment, the expressions of the Notch1, Hes1, and Hey1 in lymphocytes of the HBO group were significantly lower than those in the control group ( P<0.05). Conclusion:HBO may improve its clinical efficacy in treating children with VE by modulating the Notch signaling pathway to shift the Th17/Treg balance toward Treg.