Method for obtaining processing reference line of casing flange surface of tunnel boring machine with shaped cross section

The invention provides a method for obtaining a processing reference line of a casing flange surface of a tunnel boring machine with a shaped cross section. The method comprises the following steps of obtaining the actual contour line of the casing flange surface of the tunnel boring machine with the shaped cross section; arranging the setting design contour line and the initial position of the actual contour line on the same plane; setting a plurality of calibrating points on the actual contour line, setting calibrating points on the design contour line to correspond to the calibrating points on the actual contour line, and obtaining a plurality of corresponding distances according to the calibrating points on the actual contour line and the corresponding calibrating points on the design contour line; changing the position of the actual contour line on the plane, and enabling the sum of squares of the distances to be minimum through a least square method, so as to obtain the position of the actual contour line and the processing reference line when the sum of squares of the distances is minimum. The method has the advantage that the actual contour line and the design contour line can be furthest coincided by the least square method, so the manufacturing error of the tunnel boring machine is reduced, and the production accuracy of the tunnel boring machine is improved.