In order to quantitatively characterize the mixing and segregation phenomenon of municipal solid waste (MSW) layer incinerated on a mechanical grate, an MSW layer model containing three different sizes of par? ticles is established based on the discrete element method, and the mixing index and segregation index are intro? duced to characterize the mixing intensity and segregation intensity. Furthermore, the influence of movable grate pro? cess parameters (movement amplitude and reciprocating frequency) on the mixing intensity and segregation speed is analyzed based on the discrete element method. The results show that the mixing of the MSW layer mainly occurs along the layer’s advancing direction as well as the height of the layer, and a binary linear relationship between mix? ing intensity and process parameters is found. The segregation of the MSW layer is related to the component size. The larger the size of the component, the more concentrated in the top area of the material layer; and a binary nonlinear re? lationship between segregation speed and process parameters is found. The conclusion above provides an effective design reference for the efficient incineration of MSW and the optimization of incineration equipment.