New theories and technology in the electromagnetic field were put forward about DC casting of Al alloys, including the fundamental research works, i.e, effects of the electromagnetic field on solidus and liquidus, macrosegregation of the main alloying elements, microstructures, content of alloying elements in grains and grain size after solidification under electromagnetic field, and also including a new process DC casting under low frequency electromagnetic field(LFEMC), which can refine microstructure, eliminate macrosegregation, increase the content of alloying elements within grains, decrease the residual stress, avoid cracks and improve surface quality, and another new process DC casting under low frequency electromagnetic vibration(LFEVC), which is a high effective method for grain refining. New theories and technology in the electromagnetic field were put forward about DC casting of Al alloys, including the fundamental research works, ie, effects of the electromagnetic field on solidus and liquidus, macrosegregation of the main alloying elements, microstructures, content of alloying elements in grains and grain size after solidification under electromagnetic field, and also including a new process DC casting under low frequency electromagnetic field (LFEMC), which can refine microstructure, eliminate the macrosegregation, increase the content of alloying elements within grains, decrease the residual stress, avoid cracks and improve surface quality, and another new process DC casting under low frequency electromagnetic vibration (LFEVC), which is a high effective method for grain refining.