In order to improve the analysis accuracy of hyperspectral remote sensing technology, the diffraction efficiency of partial structural errors of rectangular gratings was analyzed by using scalar diffraction theory. The influence of grating local period and slit width error on diffraction efficiency was calculated. The results show that, when the processing error makes the local slit width of grating wider, the main maxima intensity (excluding zero order) of the grating decreases. This error has a relatively small effect on the intensity of the diffracted light at ±1 order. With the increase of the error, the higher the diffraction order, the faster the intensity of the light decreases. With the increase of the error, relative to the effect on ±1 order diffraction light, the higher the order, the faster the principal maximum diffraction intensity increases. This study provides a reference for the control of local period and slit width error in processing rectangular gratings.