In order to calculate the correlation between total and free PSA, data among 69 /1038 patients were further analyzed through statistical program software package for data analysis.Conclusions: Measuring serum free PSA concentrations along with PSA concentrations may provide higher accuracy for detecting prostate cancer and might eliminate unnecessary biopsies in the men with PSA of more than 4.0 ng/mL. The gene discussed is KLK3; the disease is prostate cancer.