This study was conducted to investigate the effectiveness and possible mechanisms of an herbal prescription, Huangqi Maxingshigan decoction (Radix Astragali, Herba Ephedrae, Almond, Gypsum Fibrosum, Radix Glycytthizae) on infectious laryngotracheitis (ILT) in chickens. One hundred and sixty one-day-old chicks were randomly allocated into four groups, housed in isolated cages of 40 birds each: groupⅠwas Huangqi Maxingshigan decoction treatment group, group II as Ding Chuan San control group, group III as the model group, and group IV as the blank control group. Except for the blank control group, other groups were challenged with infectious laryngotracheitis virus via the intratracheal route on age day 52. Birds in group I were administered Huangqi Maxingshigan decoction at a concentration of 0.4 mL, or with Ding Chuan San in group II for comparison at 48 h post virus challenge (day 54) when they showed clinical signs, 2 times daily for 5 days consecutively. Then, the superoxide dismutases (SOD) activity and malondialdehyde (MDA) contents in serum, the expression of IFN-γ, IL-4 mRNA in spleen, the sIgA contents in tracheal fluid, the sIgA secreting cells in trachea were determined on day 5, day 15, day 25 post infection. The results showed that Huangqi Maxingshigan decoction could correct Th2-dominant Th1/th2 imbalance through up-regulation of IFN-γ, and down-regulation of IL-4 at the transcriptional level, enhance cell-mediated immunity, ease inflammatory responses caused by ILTV. The results also showed that Huangqi Maxingshigan decoction provide an important antioxidant defense in the process of anti-ILT. Furthermore, it could induce the production of sIgA to enhance mucosal immunity.