This article presents the partial dynamic balancing of a 6-DOF (degree of freedom) haptic device. At first, the motion of the 3-DOF rotational part is decoupled with the motion of the 3-DOF translational part, because the former has no effect on the baseplate, so it can be considered as a whole and only discusses the 3-DOF translational part in the process of calculating dynamic balancing. The main feature of this mechanism is that the system is symmetric about the Cartesian coordinate, so the dynamic balancing of the 3-DOF translational part can be simplified to the dynamic balancing of 1-DOF translational part. The conditions of shaking force balancing can be obtained by keeping the linear momentum constant, and the conditions of shaking moment balancing can be get by minimizing the rate of the angular momentum. Finally, simulation examples are given to verify that the centre of mass of the partial dynamically balanced mechanism is fixed, and the global reaction forces on the baseplate are zero, and the global reaction moments on the baseplate decrease about five times at all times and for arbitrary trajectories.