Abstract: Liver transplantation is the most effective radical treatment for hepatocellular carcinoma (HCC), especially for patients with HCC complicated by cirrhosis. Since most patients are in an advanced stage of unresectable state when they are present, the preoperative downstaging treatment for liver transplantation in HCC is of great significance for increasing the opportunity for surgery, reducing the dropout rate from the liver transplant waiting list, and thereby lowering the postoperative recurrence rate. Currently, immune checkpoint inhibitor (ICI)-based combination immunotherapy and targeted therapy is the most effective treatment for preoperative downstaging in liver transplantation for HCC. However, the immunoenhancing effects of ICI may increase the risk of post-transplant rejection. Therefore, it is necessary to find a "critical point" that allows ICI to effectively inhibit tumor growth during preoperative downstaging treatment without causing severe rejection after transplantation. This article reviews the latest advances in preoperative ICI treatment protocols, efficacy assessment, indications, contraindications, drug discontinuation timing, and principles of prevention and treatment of rejection in liver transplantation for HCC.