In order to control stability of molten metal surface during electromagnetic continuous casting, the stabilities of melting surface under applications of an alternating magnetic field and a compound magnetic field were investigated experimentally. The melting surface behavior of the Sn–32%Pb–52%Bi alloy with low–melting point was measured by using a laser displacement sensor and visualized by using a high–speed video camera. The Fourier analysis method was introduced to reveal the fluctuation characteristics of free surface. It is experimentally found that when only alternating field is applied, the free surface keeps fluctuating. However, with increasing the alternating magnetic flux density, two statuses of the free surface, the stable camber deformation and the swinging phenomenon, can be observed orderly, and during swinging, the square–like or triangular prism–like deformations appear stochastically. The Fourier analysis indicates that the dominant fluctuation frequency at free surface center increases with increasing the alternating magnetic flux density. After simultaneously superposing a transverse static magnetic field within 0—1.44 T, the unstable swinging behavior of free surface can be remarkably controlled. Increase of static magnetic flux density can make the swinging amplitude reduce. Also the static magnetic field can effectively damp the free surface fluctuation. The stretch phenomenon was observed due to application of high static magnetic field in compound field, also a series of regular surface fluctuations appeared on free surface. There is an appropriate range of the static magnetic flux density to obtain more stable free surface, lower fluctuation amplitude and dominant fluctuation frequency.