Aim To study and search for a new method to solve NC programming problem about listing contour parts. Methods Put forth a self adaptive calculation method of generating automatically the paths of cutting tooltip in variable step according to the processing precision of parts. Results The calculating method can change the step readily according to the curvature variation of listed curves and meet the demand tolerance. Conclusion The calculation result show that the number of interpolated points can increase with the enhancement of finish precision and the increment of curvature auto matically.