A new 6DOF parallel manipulator with three chains was proposed. The reference system and DOF characteristics of the manipulator were introduced briefly. Based on the principle of virtual work and the kinematics model, the dynamic model of the parallel manipulator was established. By combing the dynamic performance index with different physical significances, the global performance index which evaluates the average performance of the parallel manipulator was established. By numerical simulation, the variation curves of the active forces and the dynamics performance index along with the geometric parameters were obtained. The research result provides a theoretical basis for the future engineering application about stability, optimal design and control of the manipulator.