<p>A transient three-dimensional (3D) comprehensive model has been developed to study the solidification and macrosegregation of electroslag remelted H13 steel. The electromagnetic phenomenon, heat transfer, two-phase flow, and solute transport during the remelting and hot topping stages are included. The growth of ingots is achieved by the dynamic layering method. The model is well validated by experimental results. The calculated results indicate that a typical V-shaped pool profile forms as the ESR ingot grows. Thermal and solute buoyancies drive a descending flow that scours the solidification front, transporting and accumulating expelled carbon towards the bottom of the metal pool. Positive segregation is observed in the central region of the solidified ingot, while negative segregation occurs in the outer region. As the slag thickness increases from 60 to 90 mm, the maximum segregation index along the central axis decreases from 0.0675 to 0.0565. This is due to the shorter local solidification time (LST), which plays a more significant role than the pool depth when assessing the impact of slag thickness on carbon segregation. Meanwhile, the ingot utilization rate for a segregation index of &lt;&#xa0;5 pct is enhanced by approximately 8 pct. The carbon range has also been effectively reduced.</p>