Objective: To study the correlation between the level of T-bet expression and liver damage in peripheral plasma cells of patients with autoimmune hepatitis (AIH) in order to provide reference for the study of pathogenesis and development of diseases. Methods: The peripheral venous blood and clinical examination data of 29 cases with AIH and 6 healthy volunteers were collected. The percentage of subpopulations of peripheral blood B cells and the proportion of T-bet⁺ cells in each subgroup were detected by flow cytometry. Plasma cells (CD19⁺CD10^-CD27^hiCD38^hi), primary B cells (CD19⁺CD10^-CD27^-IgD⁺), transitional B cells (CD19⁺CD10⁺), and memory B cells (CD19⁺CD10^-CD27⁺IgD^-) were the included subsets of B cells. Serum immunoglobulin G (IgG) and alanine aminotransferase (ALT) levels, the proportion of B cells in peripheral blood subsets and IgG level, the proportion of T-bet⁺ cells in each subset and the proportion of T-bet⁺ plasma cells in each subset in B cells, the proportion of T-bet⁺ plasma cells and the level of serum ALT were analyzed for correlation analysis. Statistical analysis was performed using two independent sample t-tests and linear regression. Results: The serum IgG level of AIH patients with abnormal ALT (19.47 ± 1.039)g/L was significantly higher than that of normal ALT patients (15.5 ± 1.069)g/L, and the difference was statistically significant (t = 2.65, P < 0.05). The percentage of peripheral plasma cells in B cells of AIH patients (2.80 ± 0.14) % was higher than that of healthy volunteers (0.73 ± 0.09) %, and the difference was statistically significant (P < 0.01). The percentage of T-bet⁺ cells in peripheral plasma cells of AIH patients (23.54 ± 1.61) % was higher than that of healthy volunteers (6.59±0.59) % , and the difference was statistically significant (P < 0.01). The correlation analysis showed that the proportion of T-bet⁺ cells in peripheral plasma cells of AIH patients was positively correlated with the proportion of plasma cells to B cells (r = 0.224 7, P < 0.01), and the percentage of peripheral plasma cells to B cells was positively correlated with the level of serum IgG (r = 0.299 1, P < 0.01). Serum IgG level was correlated with the level of ALT, reflecting an indicator of liver damage (t = 2.65, P < 0.05). Conclusion The increase of T-bet expression in the peripheral plasma cells of AIH patients is associated with liver damage, which is a new mechanism of AIH pathogenesis and disease progression.