Abstract <p>To clarify the influence of equiaxed grain sedimentation on solidification structure and solute segregation in wide-thick slabs, a three-phase solidification model coupling equiaxed grain sedimentation and strand electromagnetic stirring (S‑EMS) was developed. The model was employed to reveal the mechanism through which equiaxed grain sedimentation affects the evolution of solidification structure and segregation, and to quantitatively evaluate the regulatory effect of S‑EMS on grain distribution. The results show that equiaxed grain sedimentation causes pronounced asymmetry in the solidification structure, with the columnar grain region on the loose side significantly larger than that on the fixed side. When the wide-thick slab with 475 mm × 2000 mm is casted with 0.4 m/min by bow-type caster, the length ratio of columnar dendrite on the loose side and fixed side (<i>L</i>_lc/<i>L</i>_fc) reaches 1.11. During the continuous casting process of wide-thick slab, the combined action of thermal buoyancy and gravity leads to “&gt;” shaped channel segregation near the left slab edges. On the fixed side, both forces act in the same direction, driving solute enriched melt to rise obliquely at approximately 45 deg. But, on the loose side, their opposite directions reduce upward flow, producing smaller channel angles. The interaction of equiaxed grain sedimentation and natural convection induces negative segregation zone formation between the centerline and the fixed side and positive segregation zone formation between the centerline and loose side. When S‑EMS is applied, the <i>L</i>_lc/<i>L</i>_fc ratio decreases markedly to below 1.06 at current intensities above 500 A, accompanied by expansion and homogenization of the equiaxed zone. S‑EMS can effectively suppress solute segregation caused by grain sedimentation in the secondary cooling zone and promotes a more uniform solidification structure.</p> Graphical Abstract <p></p>