Method of compensating orthogonal degree of length measuring device and length measuring device using the same

The invention provides a method of compensating an orthogonal degree of a length measuring device and the length measuring device using the same. The method comprises the following steps: step 1, providing a measuring machine table and multiple alignment marks, wherein the measuring machine table comprises a frame, a rectangular measuring platform arranged on the frame, a measuring microscope arranged above the measuring platform, and a laser arranged on the frame and connected with the measuring microscope; step 2, installing the alignment marks on the measuring platform, and recording coordinates of the alignment marks corresponding to a coordinate system of the measuring platform as reference coordinate values; step 3, reading real coordinate values of the coordinates of the alignment marks corresponding to the coordinate system of the measuring platform as actual coordinate values through the measuring microscope, and comparing the real coordinate values and the reference coordinate values; and step 4, if the real coordinate values and the reference coordinate values have deviation, correcting the real coordinate values so as to cause the real coordinate values to be equal to the reference coordinate values.