Prostate antigen is a specific protein contained in prostate fluid and semen, which exists only in prostate tissue and is named prostate-specific antigen. Prostate antigen is secreted by the epithelial cells of the prostate gland, and its main physiological function is to prevent the coagulation of semen. Under normal circumstances, prostate-specific antigen is secreted by the epithelial cells of the prostate gland into the prostate ducts, and there is a blood-epithelial cell barrier in the normal prostate ducts, which prevents prostate-specific antigen from entering into the bloodstream and maintains a low concentration of prostate-specific antigen in the blood. Prostate cancer can destroy the blood epithelial cell barrier, leading to the entry of prostate-specific antigen into the blood. The higher the malignant degree of cancer, the greater the destruction of prostate tissue, and the higher the concentration of prostate-specific antigen in the patient’s serum.