Abstract: Antibiotic exposure-induced dysbiosis of the intestinal flora increases the risk of developing allergic rhinitis. Hence, regulating the balance of intestinal flora may be useful for preventing and treating allergic rhinitis. However, the underlying mechanism is unclear. Dendrobium nobile (Shihu) exhibits anti-inflammatory and immune activities. Hence, in this study, we investigated the mechanism via which Shihu may improve allergic rhinitis. Mouse models of allergic rhinitis with intestinal flora dysbiosis (Model-D, antibiotics induce intestinal flora dysbiosis with ovalbumin-induced allergy) and normal intestinal flora with allergic rhinitis (Model-N, ovalbumin-induced allergy) were established. The effect of Shihu on intestinal flora and inflammation caused during allergic rhinitis were analyzed. Allergic symptoms, infiltration of hematoxylin and eosin in the lungs and nose, and the release of various factors interleukin (IL)-2, IL-4, IFN-γ, IL-6, IL-10, and IL-17 in the lungs were evaluated. The results indicate that intestinal flora dysbiosis exacerbated lung and nose inflammation in allergic rhinitis. However, treatment with the Shihu extract effectively reversed these symptoms. Besides, the Shihu extract inhibited the PI3K/AKT/mTOR pathway and increased the level of Forkhead box protein in the lungs. Additionally, the Shihu extract reversed intestinal flora dysbiosis at the phylum and genus levels and improved regulator T cell differentiation. Furthermore, in the Model-D group, the Shihu extract inhibited the decrease in the diversity and abundance of the intestinal flora. Screening was performed to determine which intestinal flora was positively correlated with Treg differentiation using Spearman’s correlation analysis. In conclusion, we showed that Shihu extract restored the balance in intestinal flora and ameliorated inflammation in the lungs of allergic rhinitis mice and predicted a therapeutic new approach using Traditional Chinese Medicine to improve allergic rhinitis.