A light-weight, compact, highly dexterous surgical robot system for performing in vivo minimally invasive surgeries that allows precise control of position and orientation of surgical tools. The surgical robot system has three rotational degrees of freedom and one translational degree of freedom and is composed of seven links joined by three gear pairs and six turning pairs. The surgical robot system maintains an open space where a surgical tool element enters the patient to avoid self-collisions within the robot system during surgeries.