Feedforward controller is one of the important components of motion controller.To effectively reduce the motion errors and improve dynamic performances of servo system,a dynamic model of open precision motion platform was presented.The effects of the feedforward controller on steadystate error,resonance phenomena and frequency characteristic were studied.The effects principles were obtained.The effects of the feedforward controller to servo system dynamics were verified by simulation and experiments.These conclusions are helpful to guide the feedforward controller optimization and setting.