By drawing patients' blood, their levels and ratios of total prostate-specific antigen (TPSA) and free prostate-specific antigen (FPSA) were measured (with the enzyme-linked immunosorbent assay), and the kits were purchased from Shanghai Tellgen Life Science Co., Ltd. (NMPA Certified No. 20153401695/NMPA Certified No. 20153401809); mean time for developing from advanced prostate cancer to androgen-independent prostate cancer and the number of affected patients were recorded. The gene discussed is KLK3; the disease is Familial prostate cancer.