Abstract: A method of designing continuous phase plates(CPP) for beam smoothing has been studied. The new CPP was obtained through adding some procedures into the traditional GerchbergSaxton(G-S) algorithm that was giving a new way of initial phase, adding steps of unwrapping and filtering in iterative procedure and aiming at controlling the spatial spectrum of focal spot. The surface of CPP was continuous and controllable, and compared to the traditional design, it could reduce the GRMS of CPP, get better focal spot shape, and depress the special frequency region’s modulation.Combined with SSD, the new CPP have the better effect for controlling focal spot than the CPP designed by “standard” method.