Synthesis of the mechanisms has been done with the angular displacements of the driving and the driven links given. However, the angular velocity and acceleration should very often be given arbitrarily by a designer in addition to the displacement curve and the mechanisms should be synthesized. The dynamic behaviour of the mechanisms is influenced by the values of the angular velocity and acceleration which were given in deciding the displacement curve, and it produces a deviation of the precision points from the displacement curve owing to the fluctuation of the input-torque, the deflection of the links, etc. In this paper, about the planner six-bar linkage, the displacement curves which satisfy the restricted values of the angular velocity and acceleration are decided and mechanisms are synthesized. And the fluctuation of the input-torque is analyzed and investigated.