Psa is a specific tumor marker for prostate cancer and is considered abnormal when the total Psa is greater than 4 ng/mL. if Psa is >10 ng/mL, especially if psa is >20 ng/mL, excluding measurement within 24 hours of ejaculation, excluding measurement after rectal examination, excluding measurement within 48 hours of cystoscopy or catheterization, etc., then prostate cancer is highly suspected and prostate puncture is required. A biopsy is needed to rule out prostate cancer. Therefore, when Psa>20ng/mL, the diagnosis of prostate cancer cannot be made directly, and it is necessary to further exclude whether the time of detection is correct, and prostate puncture biopsy is needed to make a definite diagnosis.