Abstract: Objective To investigate the diagnostic value of serum total prostate specific antigen（T-PSA）,free PSA（F-PSA） and their ratio for prostatic cancer. Methods Serum T-PSA and F-PSA levels were measured by ECLIA,and F-PSA/T-PSA ratio was calculated in 48 patients with prostatic cancer,46 patients with benign prostate hyperplasia（BPH） and 86 controls,respectively. Results The serum T-PSA level was significantly higher in patients with prostatic cancer than in those with BPH and in healthy individuals（P＜0.01）,whereas the level of F-PSA/T-PSA was much lower in patients with prostatic cancer than in those with BPH and in healthy individuals（P＜0.01）.The level of T-PSA in prostatic cancer patients was positively correlated with prostatic cancer stages（r=0.786,P＜0.001） and significantly higher in patients with Ⅲ-Ⅳstage of prostatic carcinoma than in those with Ⅰ-Ⅱstage of prostatic carcinoma,while the F-PSA/T-PSA ratio was not correlated with prostatic carcinoma stage（P＞0.05）. Conclusion T-PSA and F-PSA have a great diagnostic value for prostatic cancer.F-PSA/T-PSA ratio can be used as an indicator in differential diagnosis of prostate cancer and BPH.