Numerical estimation has been conducted to analyze the motion of inclusion considering the effects of argon gas injection and magnetic field application in the continuous casting of slab. The fluid velocity field was obtained by solving the Navier–Stokes equations with electromagnetic force, and the trajectories of inclusion particles are calculated based on the computed velocity field. A reasonable agreement between numerical and experimental trajectory for single sphere was obtained using the water model. The movements of particles are traced in cases with and without the magnetic field and argon gas injection. The results show that some particles after spiral movements re-enter the jet zone of molten steel, and then enter the opposite circulation zone. Inclusions in the upper circulation zone are easily removed. Argon gas injection increases the removal rate of inclusions. The spiral trajectories of inclusion particles disappear when the magnetic field is applied, and the particle velocities decrease significantly. The argon gas injection and magnetic field application are effective for the control of the inclusions.