A beam smoothing scheme for multi-color laser quad based on combination of hybrid gratings is proposed, which can achieve a combination of transverse and rotary moving of the speckles on target plane. The physical model of the transverse moving speed of the speckles on target plane is built up, and the analytical expression for the transverse moving speed of the speckles on target plane is also derived. Furthermore, the variation of the transverse moving speed of the speckles on target plane is discussed. On the basis, the influences of different combinations of hybrid gratings on irradiation uniformity on target plane are analyzed, and the parameters of hybrid gratings are optimized. Results indicate that, compared with the traditional scheme of smoothing by spectral dispersion based on linear gratings, the moving speed and direction of the speckles on target plane are more complicated based on hybrid gratings, resulting in the further improvement of the smoothing effect. Compared to the typical schemes of beam smoothing, the optimized scheme of beam smoothing for multi-color laser quad based on the combination of hybrid gratings can effectively improve the irradiation uniformity and reduce the ratio of hot spots. Additionally, the power spectral density is proposed and used to preliminarily analyze the longitudinal intensity distribution characteristics of laser quad, and it is found that the beam smoothing for multi-color laser quad based on the combination of hybrid gratings can effectively decrease longitudinal peak intensity of laser quad.