Objective：To investigate the expression and clinical significance of Yes-associated protein（YAP） in tissues of prostate can－cer（PCa），pericarcinoma（PC） and benign prostate hyperplasia（BPH）. Methods：Expression of YAP protein of 32 cases of PCa，15 cases of PC and 15 cases of BPH was investigated by immunohistochemistry. Moreover，different expression of YAP protein of 15 cases of PCa and its corresponding PC tissues were confirmed by Western blot. Results：Rate of YAP positive staining（78.13%，25/32） in PCa tissues was higher than that in PC tissues（26.67%，4/15） and YAP positive staining was not seen in BPH tissues. Staining differences between each group were statistically significant（P=0.000）. Furthermore，different expression of YAP protein was relevant with clinical stage and degree of differentiation（P=0.019，P=0.012）. The higher the clinical stage，the higher the Gleason score and YAP positive staining rate. Western blot demonstrated that YAP protein expression was higher in 15 cases of PCa（0.723±0.084） than in corresponding PC tissues（0.455±0.161），with statistically significant differences（P=0.006）. Conclusions：Expression of YAP protein is significantly higher in PCa tissues than in non-tumorous tissues，demonstrating obvious tumor specificity in PCa. YAP may be a new target in the diagnosis and treatment of PCa.