This paper introduces the machining principles and characteristics of form grinding cylinder gear as well as the solution process of circular arc and continuous least squares circular arc. after the profile shape of grinding wheel is dispersed into n discrete points using a mathematical model, discrete points are fitted with continuous arc instead of least square circle arc, which solves the smoothing problems and approximation accuracy in dressing the axial profile shape of grinding wheel used for numerical control form grinding cylinder gear. The example illustrates the method is effective in the use?