In order to study the grinding technology of Isometric Polygonal Profile (IPP), NC grinding accessory of IPP is developed, which is driven by Program Logic Controller (PLC) and step-motors. On the basis of the principle of coordinate conversion and envelope curve, formative motions of IPP are discussed in detail. Because the relationship between the rotation of parts and synchronization motion in both x and y axes of coordinates frame is of the proportional transmission, and the synchronization motion is harmonic motion in both x and y axes of coordinates frame, the relationship of them is of the proportional transmission too, but the frequency of the synchronization motion is low and the displacement is small, so the eccentric mechanism is used in the grinding accessory. The grinding process of three axes linkage of IPP can be translated into process of two axes linkage between three coordinates on machine tools by means of combination of PLC and the eccentric mechanism. It has been found by grinding experiment that the NC grinding accessory is available used for grinding IPP and other polygonal profile.