Abstract: Form-milling cutter is widely used in machining of sculptured surfaces, but its design is quite difficult.This paper is aimed to utilize the concept of rate of conformity between the generating surface Tand the sculptured surface Pto be machined in differential vicinity of the cutter contact point K, the principle of envelope and inverse envelope theorem to develop a systematic model for designing formmilling cutter.This model is based on the DG?K approach, including model of generating surface Tof cutting tool, model of helical cutting edge and actual obtained groove surface. Moreover, the visualization of helical cutting edge and helical groove surface according to the established model is also presented.The proposed method can be used as a fundamental method for form-milling cutter design.