<p>As a key operation in the bulk processing, particle mixing plays a crucial role in multiple industrial fields. In this study, the discrete element method (DEM) is used to investigate the mixing characteristics of non-spherical particles in a horizontal high shear mixer. Through quantitative analysis of Lacey mixing index, the effects of key parameters such as aspect ratio, particle shape, and rotational speed on mixing performance are discussed. The results show that the radial mixing efficiency of particles is significantly better than the axial mixing efficiency, and both increase with the increase of rotational speed. In addition, the mixing efficiency has a significant correlation with the flow resistance and energy transfer efficiency of particles. Specifically, in the axial direction, the hexahedral particles have the highest mixing efficiency, and the oblate spheroidal particles with AR = 0.25 have the lowest efficiency. In the radial direction, the hexahedral particles still maintain the highest efficiency, while the spherical particles with AR = 1 have the lowest efficiency.</p> Graphical Abstract <p></p>