Medical robotic system is a reliable method to provide a precise and safe treatment to the patients, especially in the area of urology. The prostate cancers are firmer than normal tissues. Therefore, physicians can detect the prostate cancer with a palpation. In this paper, we developed a robotic system to detect prostate cancers using robotic palpation to find the suspected area of the tissue as well as to localize the area of the needle biopsy. To validate the performance of the developed system, the experiment on soft tissue phantoms was carried out. The results indicate that the system can identify the differences of tissue phantoms within and without inclusions. In addition, the bigger inclusions and the closer inclusions from the surface show larger value of the force response. These results indicate that the developed robotic system can be used to find hard materials such as tumor and malignant tissue in the prostate.