A rotational joint has been designed and fabricated by making use of the advantages of the dielectric electro-active polymer(EAP) material. On the basis of dielectric EAP’s deformation theory, a cylindrical actuator has been designed and manufactured. The maximum displacement of 11mm has been attained and the elongation strain of active area has been up to 33.8%. Also, the actuator’s output force’ displacement characteristics have also been tested. The rotational joint driven by this type of actuator can achieve the rotation angle of about±13°,and the torque of 19.6mN•m. The rotational joint has been used to a crawling robot, and the experiment result has been analyzed.