Serum PSA is a specific marker for prostate cancer, and it is important for the diagnosis of early asymptomatic prostate cancer. Normally, PSA is a serine protease produced by the prostate epithelium, a glycoprotein secreted directly into the prostate ductal system. Its normal function is to aid in the hydrolysis and liquefaction of semen clots and is associated with male fertility. A blood-epithelial barrier exists around the normal prostatic ductal system that prevents PSA produced by the prostatic epithelium from entering the bloodstream directly, thus maintaining a low concentration of PSA in the blood. It is generally accepted that a serum PSA of less than 4.0 ng/ml is normal, and a PSA of more than 10 ng/ml increases the risk of developing precancerous cancer. When cancer occurs in the prostate gland, the blood-epithelial barrier is destroyed and more PSA is secreted by the cancer, resulting in PSA entering the bloodstream directly. The gold standard for tumor-free status after radical prostate cancer surgery is zero PSA. Since almost all of the PSA in the serum is produced by prostate epithelial cells, if all prostate tissue is removed during radical prostate cancer surgery, the PSA in the serum will drop to zero within 1 month if the tumor is eradicated. The half-life of PSA in the serum of patients with prostate cancer after surgery is 33 hours. According to this calculation, if PSA is 20ng/ml in 1 patient before surgery, PSA should be undetectable 12 days after surgery; if it is 10ng/ml before surgery, it will take 10 days; if it is 4ng/ml before surgery, it will take 8 days. Serum PSA can also be elevated in non-malignant lesions of the prostate: inflammation of the prostate, prostate hyperplasia, acute urinary retention, and prostate massage can increase PSA, but it can normalize when the causative factors are eliminated. Serum PSA can increase 1-fold after rectal examination, 4-fold after cystoscopy, and 53-57-fold after prostate puncture biopsy or transurethral electrodesection of the prostate. The PSA can also be increased by ejaculation in the normal state. Therefore, PSA testing should not be performed until one week after the anal examination and at least 6 weeks after prostate biopsy and puncture. The elevated PSA caused by cancer is persistent and continues to rise as the tumor progresses. In addition to PSA, there is prostatic acid phosphatase (PAP), an enzyme secreted by the prostate gland. In normal cases, PAP rarely enters the bloodstream; in prostate cancer, malignant cells produce PAP and it enters the bloodstream. The normal value of serum PAP is less than 3.5 ng/ml. It is currently believed that PAP has a limited role, but is considered another independent predictor of treatment failure after radical prostate cancer surgery, although it does not predict staging or other surrounding organs. Prostate specific photase (PSP ) and Prostate specific membrane antigen (PSMA), as the expression of PSMA in prostate cancer epithelial cells is not affected by the degree of tumor cell differentiation and remains high after debulking. The detection of PSP and PSMA is more meaningful than PSA or PAP, and this index has a certain clinical value for the early diagnosis of prostate cancer and the evaluation of recurrence and progression.