A grating measuring module includes a light source, a collimating device, a first grating, a second grating, and an image sensing chip. The first grating is arranged on an optical path of the collimating device and the second grating is arranged on an optical path of the first grating. Each of the two gratings comprises a first pattern and a plurality of second patterns locating at the both sides of the first pattern. The first and second gratings can each be attached to an object which may be displaced in relation to another object, so allowing light of a certain pattern to pass depending on the magnitude of the displacement. The image sensing chip arranged on an optical path from the second grating receives light emitted from the light source and forms an image from which a displacement can be calculated and displayed.