The majority of donor organs for organ transplantation in China are derived from unrelated unrelated donors, and there are differences in transplantation antigens (HLA) between donors and recipients, making it clinically difficult to find a donor organ that is identical to the recipient’s HLA, except for organ transplants between siblings. Therefore, post-transplant rejection is inevitable, and the lower the degree of HLA compatibility between donors and recipients, the greater the likelihood of rejection. In order to effectively prevent and treat graft rejection and enable long-term functional survival of the graft, transplant patients need to take immunosuppressive drugs for a long time after surgery. Currently, the main immunosuppressants commonly used in the clinic are: cyclosporine A (CsA), prochlorperazine (FK506), primidone (MMF), rapamycin (RPM), azathioprine, prednisone, etc. Among them, cyclosporine A, prochlorperazine, azathioprine and prednisone are the most commonly used immunosuppressants. Among them, immunosuppressants such as cyclosporine A, Proclovir, primidone and rapamycin have obvious individual differences in bioavailability and pharmacokinetics, etc. The sensitivity and tolerance of immunosuppressants are not the same in different patients, and even in the same patient at different times there may be variations, that is to say, even when taking the same dosage of immunosuppressant drugs, the blood concentration in different patients is not identical, or even several times different. even several times. Therefore, the types and doses of drugs taken by different transplant patients are not exactly the same, and the dose of immunosuppressive drugs must be adjusted according to the patient’s blood concentration, so as to provide a reference for clinicians to formulate a scientific and reasonable personalized drug plan for each patient. If the blood concentration is too high, toxic reactions (such as hepatotoxicity, nephrotoxicity, neurotoxicity, etc.) are likely to occur, resulting in increased transaminases, bilirubin, blood creatinine and other indicators; blood concentration is too low and easy to rejection (acute rejection, chronic rejection, etc.), resulting in the transplantation of the kidney enlargement, reduced renal function, and so on. Therefore, regular postoperative monitoring of blood drug concentration in transplant patients not only helps clinicians to guide patients to use drugs rationally, reduce the incidence of drug toxicity and graft rejection, and improve the long-term survival rate of grafts; it also helps to reduce the economic burden of patients and avoid unnecessary waste.