PSA, also known as prostate-specific antigen, is a tumor marker specific for prostate cancer. PSA is a serine protease secreted by the prostate duct epithelium and is tissue specific, so it can be clinically important for the diagnosis of prostate cancer. Generally speaking when PSA is significantly increased, it often indicates the possible presence of prostate cancer and patients often need further tests to determine the diagnosis. In addition to PSA, the diagnosis of prostate cancer can also be made through rectal examination, prostate MRI and prostate puncture biopsy. Among them, prostate puncture biopsy is the gold standard for prostate cancer diagnosis. If an abnormally high PSA is found, prostate puncture biopsy is needed to confirm the diagnosis.