<p>Carbon segregation severely affects the mechanical properties of W9Mo3Cr4V high-speed steel (W9 HSS) during the electroslag remelting (ESR) process. To predict carbon segregation in ESR with a vibrating electrode, a transient two-dimensional model was developed that couples multi-physical fields. The Joule heating and electromagnetic forces are calculated by solving Maxwell’s equations employing user-defined functions. The volume of fluid (VOF) model and dynamic meshing method are employed to simulate metal droplet motion and track the slag–metal interface. Solidification is explicitly solved using the enthalpy-porosity method, while the Lever algorithm is employed to control solute redistribution under non-equilibrium conditions and account for interactions among different elements within the ingot. Results show that the vibrating electrode can generate smaller metal droplets, which have high dropping velocity, leading to a more uniform temperature distribution in the slag pool and mitigating carbon segregation. Compared with a conventional electrode, the average positive segregation index in ESR ingots decreases by 12.62 pct (from 0.095 to 0.083), while the average negative segregation index increases by 10.25 pct (from −&#xa0;0.1204 to −&#xa0;0.108). Moreover, increasing the tungsten mass fraction from 8.5 to 9.5 pct intensifies carbon segregation: the maximum positive segregation index at the ingot center rises by 5.46 pct (from 0.2618 to 0.2761), and the maximum negative segregation index decreases by 8.28 pct (from −&#xa0;0.1938 to −&#xa0;0.2113).</p>