Prostate cancer is the most common tumor in Europe and the United States, but in recent years the incidence rate in China has increased significantly, which may be related to the westernization of lifestyle and the improvement of diagnosis. The normal value of PSA: 1, ≤4μg/L for healthy men under 40 years old (including 40 years old); 2, 97% of healthy men over 40 years old are 0-4μg/L, about 3% are 4.01-l0μg/L; 4μg/L is the threshold value for prostate cancer diagnosis. 3.When PSA≤4μg/L, only a very, very small number of people are prostate cancer. 4. When PSA>4μg/L, it should be judged together with the percentage of free PSA (fPSA) at the same time. The higher the fPSA, the less the possibility of prostate cancer, and vice versa, the lower the fPSA, the more the possibility of prostate cancer.