Recently, with the improvement of non-integer order calculus theory, fractional order calculus receives more and more attentions in the application of controlling. Especially, the fractional order PI^λD^μ controlling is applied in many fields. For the traditional PD controller which is usually used in motion control system, a kind of designing and tuning method of PD^μ controller is proposed. Since there is explicit corresponding relation between phase margin and overshoot of the designed system, by designing the rate of change of phase the system’s phase can be made stable around cut off frequency and the influence of open loop gain’s variations on the overshoot can be reduced. Cut-off frequency ω_c and phase margin γ_m given are considered as design specifications in this method. PD^μ’s derivation order μ and derivation coefficient K_d can be derived from system’s phase equation and rate of change equation. Proportional coefficient K_p can be obtained from the magnitude equation on the cut off frequency. Finally, this method is applied to a linear motion control experiment platform. By simulations and experiments comparing with integer order ITAE-optimal method, the effectiveness and excellence of this method is verified. From the results, it can be noticed that the controlling system designed in this method has a good inhibition effect on the overshoot variations caused by the fluctuations of the system parameters on the premise of meeting the design specifications. 