To determine the effect of dexamethasone on regulating the TGF-β1/Smad3 signalling pathway in airway remodelling model of asthmatic rats.An experimental study.Department of Pathology, The First Hospital of Wuhan, Hubei Province, China, from February 2017 to April 2018.Thirty male SPF Sprague-Dawley rats were randomly divided into the control group, the model group and the dexamethasone group, with 10 rats in each group. Rats were sensitised and excited by ovalbumin (OVA) to establish the model of bronchial asthma. The bronchial basement membrane perimeter (Pbm), the bronchial wall thickness (Wat), the smooth muscle thickness (Wam), collagenous fiber thickness (Wac) and other airway remodelling indices were measured and calculated by image analysis system. The expressions of TGF-β1 and Smad3 mRNA and protein in lung tissue of each group of rats were detected by RT-PCR and Western blot.Wat/Pbm, Wai/Pbm and Wam/Pbm in the model group were higher compared with those in the control group (all p<0.001); Wat/Pbm, Wai/Pbm, and Wam/Pbm in the dexamethasone group were significantly lower than those in the model group (all p<0.001). Relative expression levels of TGF-β1, Smad3 mRNA and protein in the model group were higher than those in the control group (all p<0.001); the relative expression levels of TGF-β1, Smad3 mRNA and protein in the dexamethasone group were lower than those in the model group (all p<0.001).Dexamethasone may antagonize airway remodeling by regulating TGF-β1/Smad3 signaling pathway, which likely to play a role in the treatment of bronchial asthma.