Abstract： Objective To observe the deposition of C4d in the liver aUograft, explore the rela-tion between Cad and liver allograft rejection, and to provide a strategy for diagnosis and therapy of the liver allograft rejection. Methods 36 liver biopsies were performed in 25 patients undergoing livertransplantation, 34 of which were enrolled in this study. The biopsy time was from 7 days to 25months after the operation. HE and immunohistochemical staining of Cad were performed in the 34liver biopsy specimens and the preoperative specimens. Results 16 acute rejections, 9 chronic rejec-tions and 9 non-rejections (3 cases of biliary duct complication, 5 cases of drug-induced hepatitis and one cases of HBV recurrence) were diagnosed in the 34 biopsy specimens. C4d was not found in thepreoperative specimens. Cad deposited in 9 of the 16 cases of acute rejection cases (9/16), 5 ofchronic rejection cases (5/9), and one case of the nonanasmotic biliary stricture in the non-rejectioncases (1/9). There was no regional difference in the Cad deposition between the rejection cases and the non-rejection cas. The positive ratio of Cad in the acute and chronic rejection group was higherthan in the non-rejection group (P<0. 05, P<0.05). The severity of hepatic injury was not related to the positive ratio of Cad. The effective power of steroid in the C4d-positive group (35.7%, 5/14)was lower than in the Cad-negative group (63.6 %, 7/11 ). Conclusion Cad could suggest theoccurrence of humoral rejection and can be used as the routinely immunohistochemical examination inliver biopsy specimens with hepatic injury after liver transplantation. Cad is helpful for monitoring theoccurrence of humoral rejection and providing the foundation for choosing the therapeutic regimen ofliver allograft rejection.