Abstract: Objective: To study the protective effect and mechanism of royal jelly acid on Con A - induced acute liver injury in rats. Methods: SD rats were randomly divided into negative control group, model control group, biphenyl diester positive control group, low, medium and high (30, 60, 120 mg/kg·bw) dose group. In order to evaluate the protective effect of royal jelly on acute liver injury induced by Con A, we studied the effects of royal jelly on liver function, combined with the changes of liver histomorphology and hepatocyte apoptosis. By analyzing the effects of royal jelly acid on inflammation, oxidative stress, hepatocyte cycle and T lymphocyte classification of spleen and peripheral blood in rats, the protective mechanism of royal jelly acid on acute liver injury was studied. Results: Compared with the model group, AST, ALT, LDH and AKP activities in the polar serum of the high-dose group significantly decreased (P<0.01); the degree of liver cell injury was improved; histopathological observation of liver showed that the groups in each dose of the royal jelly were significantly decreased (P<0.01); IL-6, IL-10, TNF-α and INF-γ in serum were significantly declined (P<0.01); the content of MDA in serum was significantly decreased and the activity of SOD and GSH-Px in serum significantly increased (P<0.01); the proliferation of hepatocytes to G₂ phase was significantly inhibited in all dosage groups (P<0.05); apoptosis rate of hepatocytes significantly reduced (P<0.01); the ratio of CD3⁺, CD4⁺ and CD8⁺ in spleen and peripheral blood significantly increased in all dosage groups. Conclusion: Royal jelly acid has protective effect on acute liver injury induced by Con A in rats. The mechanism may be related to the inhibition of inflammation, antioxidation and improvement of immune function.