The precision of the groove density influence the dispersion and the diffraction of gratings and the configuration of the spectrograph. In order to improve the precision of the groove density of the plane holographic gratings, a method of adjusting the groove density spatial frequency multiplication of plane holographic grating is proposed. A reference grating with a specific groove density is set in the exposure area. Adjusting the interference angle, different orders of the two diffraction wavefronts match and form Moiré pattern at the screen in a special orientation. The groove desity multiple of the reference gratings can be obtained. The relation between the period of the reference grating and the interference fringe pattern is proved in theory. The equation regulation of the reference grating for groove density alignment is pointed out. The precision relation between the groove density of the interference fringe pattern and the width of the reference grating is also analyzed. The results indicate that the precision of the groove density of adjusting is less than 1 nm at the 100 mm width of the reference grating for 300 line/mm groove density alignment; the error decreases with increasing the width of the reference grating. The method of adjusting the groove density spatial frequency multiplication of plane holographic grating based on the groove density of the reference grating satisfies the fabrication requirement.