The influence of the grating on the spectrometer table which rotated a certain angle on the change of diffraction angle is analgzed theoretically，and through the Matlab software to make surface chart which can visually observe the change of diffraction angle as you increase the rotation angle and the diffraction angle． Compared the experimental measurements with theoretical derivation，found that the grating rotated a certain angle，the change of diffraction angle used in the calculation increases with the increase of the diffraction angle，and it will cause some errors in the calculation of wavelength．