Abstract: In this paper, method for dealing with the following problems in computer graphics NC programming. （ 1 ） The control structure of tool path-offsetting program, and the user friendly interface of control parameter communication area are described, which make the schedule of program and the input or modification of control parameters more flexible and convenient; （ 2 ） The algorithms for end-milling and side-milling tool location computing are offered, including the way to check and correct the interference or collision between tool and control surfaces; （ 3 ） Also given are the methods for finding the cutter location at boundary or corner between control surfaces, and detecting the errors occuring at the corner with the help of adjoining relation between corners. The methods given above, are considered to be of great improtance in the practice of computer graphics NC programming for parts with sculptured surfaces.