Objective： To measure the percent of free prostate specific antigen（fPSA） among men without prostate diseases in Xi’an area， and to study the relationship of percent fPSA with age and pathological grade， clinical stage of prostate cancer（PCa） with percent fPSA， and to analyze the difference between the data in China and the overseas data to determine appropriate reference range for Chinese male. Methods： A total of 713 participants were enrolled into the study， with PSA， fPSA in serum measured and the percent fPSA calculated. Out of 713 cases， 679 without prostate diseases were divided into 5 groups by age， and then the relationships of PSA， fPSA and percent fPSA with age were studied， respectively. The relationship of pathological grade and clinical stage with percent fPSA of the 34 participants with PCa was also studied. With the help of the related data of men without prostate disease， the appropriate reference range for Chinese male was established. Results： The increases in PSA or fPSA were correlated with age， while there was no significant correlation between age and percent fPSA. The percent fPSA was also correlated with pathological grade and clinical stage of PCa. The percent fPSA of men without prostate disease in Xi’an area was significantly lower than that in the related overseas data. The reference range of percent fPSA for Chinese male was≥15%. Conclusion： Percent fPSA might be more useful than PSA in the detection of prostate cancer. As the percent fPSA is decreased， the pathological grade is decreased， and the clinical stage is increased， the malignant degree is increased. The reference range of ≥15% is more appropriate for Chinese male.