ObjectiveTo observe the effects of Yifei Tongluo prescription on the NOD-like receptor protein 3 （NLRP3）/Caspase-1/gasdermin D （GSDMD） pathway and epithelial-mesenchymal transition （EMT） in rats with pulmonary fibrosis. MethodsTracheal instillation of bleomycin was conducted to establish a rat model of pulmonary fibrosis. Thirty Sprague-Dawley （SD） rats were randomly divided into a blank group， a model group， a prednisone acetate group （1.17 mg·kg^-1）， and low- and high-dose Yifei Tongluo prescription groups （10.62 and 21.24 g·kg^-1， respectively）. Administration started on the 7th day after modeling， once a day for 28 consecutive days. The lung coefficient of each group was calculated. The pathological changes of lung tissues in each group were observed by hematoxylin-eosin （HE） staining and Masson staining. The expression of α-smooth muscle actin （α-SMA） and vimentin in rat lung tissues was detected by immunohistochemistry. The expression of NLRP3 inflammasome， E-cadherin （E-cad）， and typeⅠ collagen （ColⅠ） in lung tissues was detected by immunofluorescence. The content of hydroxyproline （HYP）， tumor necrosis factor （TNF）-α， interleukin （IL）-18， and IL-1β in rat serum was detected by enzyme-linked immunosorbent assay （ELISA）. The mRNA expression levels of NLRP3， apoptosis-associated speck-like protein containing a CARD （ASC）， IL-1β， and transforming growth factor （TGF）-β₁ in rat lung tissues were determined by real-time quantitative polymerase chain reaction （Real-time PCR）. The protein expression levels of NLRP3， GSDMD， ASC， and Caspase-1 in rat lung tissues were determined by Western blot. ResultsCompared with the blank group， the model group exhibited a significantly increased lung coefficient （P<0.01） and significantly increased range of pulmonary interstitial inflammation and collagen deposition. In addition， the levels of α-SMA， Vimentin， E-cad， and ColⅠ in lung tissues were significantly increased （P<0.01）. The levels of fibrosis- and inflammation-related factors HYP， TNF-α， IL-18， and IL-1β in serum were significantly upregulated （P<0.01）. The levels of factors related to the activation of NLRP3 inflammasome in lung tissues， including NLRP3， GSDMD， ASC， Caspase-1， IL-1β， and TGF-β₁， were significantly upregulated （P<0.01）. Compared with the model group， the Yifei Tongluo prescription groups showed improved lung coefficients. Additionally， the extent of lung inflammation and collagen deposition was significantly reduced. The expression of α-SMA， Vimentin， E-cad， and ColⅠ in lung tissue was significantly decreased （P<0.01）. The levels of HYP， TNF-α， IL-18， and IL-1β in serum were significantly reduced （P<0.01）. The expression levels of NLRP3， GSDMD， ASC， Caspase-1， IL-1β， and TGF-β₁ in lung tissue were also significantly decreased （P<0.01）. ConclusionYifei Tongluo prescription can regulate the NLRP3/Caspase-1/GSDMD pathway， down-regulate release of pro-inflammatory and pro-fibrotic cytokines， alleviate NLRP3 inflammasome-mediated pyroptosis and EMT， and thereby improve pulmonary fibrosis in rats.