This paper proposed an simply and effectively dynamic model for the spatial 6-DOF parallel manipulator with heavily eccentric payload (PMHEP). Based on Newton method and theorem of angular momentum, the mathematical model of the PMHEP is derived, viewing it as a rigid body. The dynamic equations are programmed and implemented in Matlab/Simulink. Simulation results verified the dynamic formulations under the presented approach, through comparing with completely dynamic model constructed with SimMechanics according to the physical relationship of PMHEP. Moreover, the dynamic equations are more simplified and efficient to be utilized in real time controller and configuration design, as well as dynamics analysis.