PSA is an abbreviation for prostate-specific antigen. f-PSA is free prostate-specific antigen and t-PSA is total prostate-specific antigen, which is a sensitive indicator for the diagnosis of prostate cancer. In general, f-PSA/t-PSA > 0.25, if the ratio is low, further judgment is needed in combination with prostate-specific antigen and the possibility of prostate cancer needs to be considered. The majority of PSA is present in the blood in a protein-bound state, with the rest being free. If the t-PSA value is 4-10 μg/L at this time, the f-PSA/t-PSA value is diagnostic. If the ratio is high, the likelihood of prostate cancer is low; if the ratio is low, with a value <0.16, the likelihood of prostate cancer is high. If the diagnosis of prostate cancer is confirmed, further treatment should be carried out under the guidance of a doctor, commonly radical surgery and removal of surrounding lymphatic tissue, and postoperative review should be carried out on time. In addition, for diseases such as prostatitis and prostatic hyperplasia, serum t-PSA will be mildly elevated, causing f-PSA/t-PSA values to be low as well, and attention needs to be paid to differential diagnosis.