It has been a significant and challenging issue to solve the inertial wrench of parallel manipulators (PMs) for their dynamics analysis and control. A CAD variation geometry approach is proposed for solving the inertial wrench of PMs. First, an initial simulation mechanism of PM, and a simulation mechanism of PM with linear/angular velocity and acceleration are created. Second, when modifying the driving dimension of the active legs, the simulation mechanisms are varied correspondingly, the position, linear/angular velocity and acceleration of moving platform and legs, and inertial wrench of moving platform and legs are solved automatically and visualized dynamically. Third, a 3-DoF PM is illustrated, and the displacement, linear/angular velocity and acceleration, and inertial wrenches of the moving platform and legs are solved using CAD variation geometry and are verified by the analytic solutions. Finally, inertial wrenches of the legs are transformed onto the moving platform.