Aiming at the detonating robot arm driven by the hydraulic motor worked in a special environment, according to the problem of poor flexibility and low precision in the working process, a Six Degrees of Freedom (6-DOF) rotating robot arm driven by a hydraulic motor is proposed to meet the working requirements under complicated working conditions. By establishing the D-H coordinate system and the three-dimensional (3D) model of the manipulator, according to the principle of the D-H coordinate system, the kinematics equation was derived from the theory, the relationship between the position of the end of the connecting rod and each angle of the joints could be obtained, and the forward kinematics and inverse kinematics simulation were carried out with MATLAB and Adams united. The varying curve of each joint angle and the curve of the end displacement were obtained. The results show that the mechanical design of the 6R manipulator is reliable and the kinematics theory equation is correct. It can meet the position requirements of the manipulator’s end space coordinate from (-160 mm, 410 mm, 740 mm) to (-502 mm, -160 mm, 362 mm).