By establishing relevant coordinates of the Automatic Laser Navigation System, the basic principle of the system which
accesses the TBM three-dimensional reference point and yawing angle by mathematical transformation between TBM,
target prism and earth coordinate systems is discussed deeply in details. According to the way of rigid body descriptions
of its posture, TBM attitude parameters measurement and data acquisition methods are proposed, and measures to
improve the accuracy of the Laser Navigation System are summarized.