A rejection reaction is an immunologic response of the body to attack, destroy, and remove the graft from the allogeneic tissue or organ transplanted into the body. Rejection reactions in lung transplantation usually include acute rejection and chronic rejection; there are usually at least three acute rejection reactions in the first three months after surgery, while chronic rejection reactions are present in most patients; mild chronic rejection reactions do not cause any harm to the patient’s life, while severe ones require another lung transplantation; acute and chronic rejection reactions are mainly distinguished by the following aspects: from the onset of the disease The diagnosis of acute and chronic rejection is mainly made by lung biopsy, and can be completed by clinical lung function monitoring. The treatment for acute rejection includes conventional maintenance therapy and shock therapy; the usual maintenance therapy of conventional drugs, commonly used drugs such as cyclosporine and hormone; shock therapy is to carry out hormone shock therapy for the determined or highly suspected acute rejection; the treatment of chronic rejection is mainly done by increasing immunosuppression; acute rejection, after a series of anti-rejection drugs, will quickly improve, while chronic rejection is lifelong The chronic rejection is lifelong. 1, Acute cellular rejection (acutecellularrejection, ACR) and lymphocytic fine bronchitis ACR is mainly produced by T cells recognizing the major histocompatibility complex of the graft and is now considered to be the main form of AR. 2, antibody-mediated rejection (antibodymediatedrejection, AMR) AMR is a rejection reaction caused by the recognition of foreign grafts and the production of donorspecific antibodies (DSA), and DSA is an important risk factor for the occurrence and development of AMR. The definition of pulmonary AMR includes circulating DSA, graft dysfunction, abnormal graft pathology, and capillary CD4 deposition. 3. chronic rejection Chronic rejection manifestations include BOS characterized by chronic small airway obstructive changes, and restrictiveallograftsyndrome (RAS) characterized by restrictive ventilation impairment and peripheral pulmonary fibrotic changes. Chronic rejection, the primary cause of long-term graft survival and chronic graft failure [17-18], occurs months or years after transplantation and manifests as progressive decompensation of graft organ function with characteristic histological and imaging changes. The presence of postoperative PGD, AR, and infection are independent risk factors for the development of BOS, and bacterial, fungal, and viral infections are associated with the development of BOS (especially Pseudomonas aeruginosa, Aspergillus, and cytomegalovirus); avoiding these complications can help reduce the incidence of postoperative BOS, and performing lung retransplantation can treat graft loss of function due to chronic rejection.