The criteria for the three index ratio for prostate cancer are serum total prostate-specific antigen (t-PSA) <4ng/ml and the ratio of free PSA to total PSA (f-PSA/t-PSA)>0.16, while the value of serum free prostate-specific antigen (f-PSA) alone is of little significance. Total serum prostate-specific antigen is the sum of serum free prostate-specific antigen and bound prostate-specific antigen and represents the total serum PSA level. Serum total prostate-specific antigen is often less than 4 ng/ml. If it is greater than 4 ng/ml and less than 10 ng/ml, there is a possibility of prostate cancer, but diseases such as benign prostatic hyperplasia, inflammation of the prostate gland, and tests such as cystoscopy and even rectal fingerprinting can lead to elevated serum total prostate-specific antigen. A combination of serum free prostate-specific antigen is needed to aid in the diagnosis. The ratio of free PSA to total PSA is often greater than 0.16. If the ratio is greater than 0.25, a benign prostate lesion is suspected and prostate cancer is less likely. If the ratio of the two is less than 0.16, the possibility of prostate cancer is high, and further ultrasound of the prostate is needed to make a clear diagnosis. It is recommended that the patient should consult a professional doctor for further diagnosis and treatment after examination.