Abstract: In order to study the diffraction characteristics of blazed gratings and analyze the influence of grating parameters on diffraction efficiency, the dependence of diffraction efficiency on the different grating structure parameters and wavelengths was obtained based on the rigorous coupled-wave electromagnetic theory. Calculation results showed that the larger the slot angle, the smaller the blazed angle and the diffraction efficiency, and the bigger the wavelength, the smaller the diffraction efficiency and the bigger the blazed angle. Finally,the polarization phenomenon of a blazed grating was analyzed. The obtained results are helpful for the grating design.