Laser remelting technique has been popularly used as a means of final surface processing. However, surface undulation after laser remelting is always a problem because it degrades the surface quality. In order to obtain a smooth surface, reduce time and cost of post-machining, a steady magnetic field can be applied to assist the laser remelting process, which suppresses the undulation. The aim of this study is to investigate the suppression effect of a steady magnetic field on molten pool during laser remelting using experimental and numerical methods. The experimental results are in good agreement with the numerical ones. These results demonstrate that the Lorentz force due to a steady magnetic field is a sort of drag force of melt flow, which significantly reduces the flow velocity. Thus, surface undulation is effectively suppressed by a steady magnetic field and smooth surface after laser remelting can be achieved. (C) 2015 Elsevier B.V. All rights reserved.