There are many reasons for high lymphocyte percentage, infectious diseases, tumor diseases, transplant rejection and other factors can lead to high lymphocyte percentage. 1. Infectious diseases: Pathogenic microbial infection is a common cause of high lymphocyte percentage, such as measles, rubella, viral cold, viral hepatitis and other infectious diseases can lead to high lymphocyte percentage. 2. Neoplastic diseases: hematologic malignant diseases such as leukemia and lymphoma and other neoplastic diseases can easily lead to high lymphocyte percentage. 3. Transplantation rejection reaction: this condition mainly occurs in patients who have undergone organ transplantation, when the transplanted organ and the patient’s body have a rejection reaction, the lymphocyte ratio in the patient’s body will be high. Different patients have different reasons for high lymphocyte percentage, patients should consult the hospital in time, early examination to clarify the specific causes of the disease, and active treatment.