Objective To investigate the expression of NLRP3 inflammatory body in the process of liver fibrosis in a rat model of common bile duct ligation (BDL) and the association of NLRP3 inflammatory body with liver fibrosis. Methods A total of 65 Sprague-Dawley rats were randomly divided into sham-operation group with 15 rats and BDL model group with 50 rats. On days 3, 7, 14, 21, and 28, 10 rats in the model group and 3 rats in the sham-operation group were sacrificed. The serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), direct bilirubin (DBil), total bilirubin (TBil), total bile acid (TBA), and alkaline phosphatase (ALP) were measured, and HE staining, Masson staining, and sirius red-picric acid staining were performed for liver tissue to evaluate liver fibrosis degree. Immunohistochemistry was used to measure the expression levels of alpha-smooth muscle actin (α-SMA) and transforming growth factor-β1 (TGF-β1) in liver tissue, Western blot and qRT-PCR were used to measure the expression level of NLRP3 inflammatory body, and ELISA was used to measure the level of the inflammatory factor interleukin-1β (IL-1β) in liver tissue. An analysis of variance was used for comparison of continuous data between groups, and the least significant difference t -test was used for further comparison between two groups. Results Compared with the sham-operation group, the BDL model group had significant increases in the serum levels of ALT, AST, DBil, TBil, TBA, and ALP (all P < 0.05) and the level of IL-1β in liver tissue ( P < 0.05), which reached the highest level on day 3 and then decreased. Compared with the sham-operation group over time, the BDL group had a significant increase in liver fibrosis score ( P < 0.05); immunohistochemistry showed gradual increases in the expression of SMA-α and TGF-β1 ( P < 0.05), and Western blot and qRT-PCR showed a gradual increase in the protein expression of NLRP3 inflammatory body in liver tissue ( P < 0.05), which remained stable after day 14. Conclusion Liver injury exists persistently in a rat model of BDL, and liver histopathology shows the dynamic evolution of hepatitis, liver fibrosis, and liver cirrhosis. NLRP3 inflammatory body is in a state of continuous activation and may play an important role in the process of liver fibrosis.