Al-8Si alloy cast-rolling strip billet was prepared by the continuous cast-rolling method, and the influences of different lengths for cast-rolling area on microstructure and central segregation for cast-rolling plate were studied by optical microscope (OM), scanning electron microscope (SEM) and energy dispersion spectrum analysis (EDS). Researches show that with the increasing of the length for cast-rolling area, the range of segregation increases first and then decreases. The increasing of length for cast-rolling area resultes in the increasing of the cooling strength for cast-rolling area, and the stronger cooling speed accelerates the solidification of molten metal to reduce the degree of central segregation. Furthermore, the morphologies of eutectic silicon on the surface and in the center of Al-8Si alloy in the same cast-rolling area are quite different. The eutectic silicon on the surface is distributed in a network, and the microscopic morphology is mostly fibrous, but a small part is petal-shaped. The morphology of eutectic silicon in the central layer is clustered along different orientations to form a middle line segregation. This is because when the cast-rolling billet is rolled, the upper and lower layers are in contact with the roll surface first, and the cooling speed of the central layer is slower than that of the upper and lower surfaces, so the central layer solidifys at last and the upper and lower surfaces have smaller grains than the center layer.