Abstract: Objective To investigate the expression of NY-ESO-1 in serum of prostate cancer patients and its relationship with Gleason score. Methods A total of 447 patients, which included 148 prostate cancer patients, 124 BPH patients and 175 healthy donors were enrolled in this study. The expression of NY-ESO-1 was detected by ELISA to determine the range of its normal values, and calculate their positive expression, specificity and sensitivity. The positive serum was verifi ed by Western blot and its relationship with Gleason Score was analyzed by statistic methods. Results The positive expression of NY-ESO-1 in prostate cancer patients and BPH patients were 48.6% and 9.6%, with signifi cant difference(P=0.021). Compared with BPH patients, the specifi city and sensitivity of NY-ESO-1 in diagnosing prostate cancer were 82.3% and 41.9%,respectively. The specifi city and sensitivity were 44.0% and 33.9%,respectively, in those patients with PSA values between 4-10 ng/ml. Spearman correlation analysis showed NY-ESO-1 and Gleason score were positively correlated(r=0.872). Conclusion NY-ESO-1 is highly expressed in prostate cancer patients, and the expression is positively correlated with Gleason score.