Objective To investigate the possible mechanism of Xiaoyao Powder（ 逍遥散） in preventing and treating acute liver injury induced by Tripterygium Wilfordii（ 雷公藤）. Methods A total of 30 SD rats were randomly divided into normal group

model group and Xiaoyao Powder group

with 10 rats in each group. In the Xiaoyao Powder group

the rats were given intragastric administration of 6. 75 g/（ kg·d） of Xiaoyao Powder for 4 days before modeling

and the normal group and the model group were given an equal volume of distilled water once a day. Rat model of acute liver injury was established in the model group of Day 5 and Xiaoyao Powder group by intragastric administration of Tripterygium wilfordii decoction 3. 75 g/（ kg·d） for 4 consecutive days. Liver index and serum alanine aminotransferase（ ALT） and aspartate aminotransferase（ AST） levels were compared between the groups

and the expression of B cell lymphoma/leukemia-2（ Bcl-2） and Bcl-2 related X protein（ Bax） protein in the liver tissue and cysteine-containing aspartate-specific proteases 3（ Caspase-3） activity were detected. Results Compared with the normal group

the liver index and serum ALT and AST levels in the model group were significantly increased. The expression of Bcl-2 protein and Bcl-2/Bax in liver tissue decreased significantly

and Bax protein expression and Caspase-3 activity increased significantly（ P < 0. 05 or P < 0. 01）; compared with the model group

liver index and serum ALT and AST levels were significantly decreased in Xiaoyao Powder group

and Bcl-2 protein expression and Bcl-2/Bax values ?? in liver tissue were significantly increased. Bax protein expression and Caspase-3 activity were significantly decreased（ P < 0. 05 or P < 0. 01）. Conclusion The prevention and control effect of Xiaoyao Powder on acute liver injury induced by Tripterygium wilfordii may be related to the up-regulation of Bcl-2 protein level in liver tissue

down-regulation of Bax protein level and Caspase-3 activity

and thus to improve hepatocyte apoptosis.