A detailed scheme by which the status of tiled gratings can be inspected in a real-time way is put forward. The He-Ne laser is shown to be inappropriate for the grating-tiling experiment where 1740/mm grating is used. A method is proposed by which the wavelength can be selected for the real-time measurement, so that the impact of all sorts of errors of the tiled gratings on the main beam(1053nm) and the beam for measurement is completely identical, which has been demonstrated by experiment.