It is able to provide a new method for the calculation of furthest right point of taper and column pro-cuts by CAD.Where taper and column pro-cuts it usually utilizes characteristic of gather in side elevation to seek the cut line in the furthest right point,passing the top of taper to make cut line of gather circularity,finding out the cutting point in shadow of V side,which was thought that the point should be the furthest right.However,it is not correct.The paper gives an accurate solution of finding the cut line in the furthest right point,and makes a analysis by analytics.