<p>The flow behavior of molten steel in the thin slab mold under high casting speed conditions was investigated, with a focus on the multi-mode continuous casting and rolling mold. A steel–slag two-phase flow model was established using large eddy simulation, the volume of fluid, and magnetohydrodynamics methods through numerical simulation. The maximum flow velocity and wave height at the steel–slag interface within the mold are critical evaluation criteria for analyzing asymmetric flow under varying casting speeds and electromagnetic braking. The results indicate that the asymmetric flows within the mold do not occur synchronously. The severity of the asymmetric flow correlates with the velocity difference across the steel–slag interface. A greater biased flow prolongs the time required to revert to a steady state. When the magnetic field intensity is set to 0.24&#xa0;T and the magnetic pole position is at 390&#xa0;mm from the steel–slag interface, this configuration can reduce the velocity of the steel–slag interface, thereby mitigating the asymmetric flow. Additionally, it can diminish the velocity, impact depth, and impact intensity on the narrow face of the jet, thus improving the distribution of velocity and turbulent kinetic energy within the mold. This configuration prolongs the time required for the steel–slag interface to transition from a stable state to its maximum velocity and shortens the time for the interface to return to stability from an unstable state. Moreover, it ensures the positional stability of the steel–slag interface, confining its position within −3&#xa0;mm.</p>