A novel four degree of freedom (4DOFs) parallel mechanism was obtained by using method of adding constraintdrivenlimb limiting the DOFs of movement platform and removing drivinglimbs. The DOFs of this mechanism were analyzed, and then the input/output relationship equations of moving links were built and NewtonEuler (NE) method was used to establish dynamical model of this mechanism including drivingjointfriction. Through the programming calculation and proposing the method of motion trajectory planning of the mechanism, the force/moment of each limbs and platforms was obtained in the two different trajectories conditions. Finally the tool kit of SimMechanics and Matlab were used to simulate this parallel mechanism dynamicaly, which verifies the correctness of theoretic calculation fot the mechanism.