In this paper, we propose a two DOF joint mechanical design scheme for heavy-load manipulator based on linear driving, the key structural parameters that directly influencing on the linear driving force is determined. Based on the multi-body kinematics and the principle of virtual work, we derive the relationship between the torque of joint space at the base of the heavy-load manipulator and the force of linear driving, then by analyzing the relationship, we obtain the design method of key structural parameters. Finally, using simulation analysis we validate this design method.