An experimental set up of travelling magnetic field excited by supper power permanent magnet was designed, which has obviously refine function for metal solidification structure. Theory of travelling magnetic field excited by permanent magnet was researched: mathematics model was built, analysis solutions of magnetic component force parallel to slab was obtained. It was confirmed that the magnetic component force was existed through round and slab of cast metal experiment. When travelling magnetic field was imposed properly during metal solidification, solidification structure of 100% fine equiaxed crystal could be obtained.