Electromagnetic field was applied by ZL201 alloy melt when it was cast in near-liquidus temperature. The effects of electromagnetic stirring power and cooling condition on microstructure were studied. The result showed that, by using electromagnetic field at near-liquidus temperature, alloy microstructures were the fine and uniform non-dendritic grains. Moreover, with current strength increasing and cooling condition strengthening, the trend of the fine and uniform reinforced. When ZL201 alloy was cast at low superheat, the radius of the critical nucleus reduced. Under electromagnetic field, the melt temperature gradient decreased, and the formation of quasi-solid phase atom clusters in the melt was promoted. So the nucleation rate increased and microstructures were fine and uniform. Electromagnetic field made solute uniform, and the rapidity of nucleus growing up in all directions was almost at the same rate, therefore, the grain grew up near-spherical shape.