Abstract: Objective: To explore the value of the prostate-specific antigen( tPSA) and its related index in the diagnosis of prostate cancer( PCa). Methods: Forty-five patients with PCa,50 patients with benign prostatic hyperplasia and 45 healthy volunteers were served as observation group,benign prostate hyperplasia( BPH) group and control group,respectively. The levels of serum tPSA and free tPSA( fPSA) were measured by enzyme amplification chemiluminescence analyzer,and the ratio of fPSA and tPSA was calculated. Results: The levels of tPSA and fPSA in observation group were significantly higher than those in BPH group( P 0. 01),the levels of tPSA and fPSA in BPH group were significantly higher than those in control group( P 0. 01). When the value of tPSA were less than 4. 0,4. 0 to 10. 0 and greater than 10. 0 g / L,BPH patients accounted for 64. 0%,30. 0% and 4. 0%,respectively,PCa patients accounted for 8. 9%,22. 2% and 68. 9%,respectively,and the healthy people accounted for 97. 8%,2. 2% and 0. 0%,respectively, the differences of there groups have statistical significance( P 0. 01). The ratio of fPSA and tPSA in observation group was significantly lower than that in control group and BPH group( P 0. 01),the ratio of fPSA and tPSA in BPH group was significantly lower than that in control group( P 0. 01). Within the 4. 0 to 10. 0 of gray area,the critical value of fPSA and tPSA in observation group and BPH group was 0. 16,the ratio of fPSA and tPSA in 80. 0% of patients of observation group was less than 0. 16,and the ratio of fPSA and tPSA in 86. 7% of patients in BHP group was greater than 0. 16,the difference of which was statistical significance( P = 0. 002). Conclusions: The tPSA combined with the ratio of fPSA /tPSA can be used as an important basis in the diagnosis of prostate cancer.