PSA refers to prostate-specific antigen, which is categorized into free PSA and conjugated PSA.There is no clear clinical rule on how much free PSA is cancerous. The normal range of total PSA is 0-4ng/mL, when the total PSA is between 4-10ng/mL, or more than 10ng/mL, further examination is needed. When the clinical blood test for prostate cancer indicators, when the total PSA value exceeds 4ng/mL, it is also necessary to look at the ratio of free PSA to total prostate-specific antigen for judgment. If the ratio is <0.16, the patient is at increased risk for prostate cancer. If the patient has an abnormal free PSA, a rectal prostate ultrasound, CT, or MRI is needed to identify the abnormality. If the patient is diagnosed with cancer, he should cooperate with the doctor for treatment in time to avoid delay.