Abstract: Simulation was made using CFD software Fluent to calculate the flow field of aluminum alloy melt sonicated in a crucible. The results showed that large-scale Eckart acoustic streaming formed in the liquid phase zone under the radiator's face, driven by radiation force which formed as a result of acoustic pressure gradient due to viscous attenuation. The maximum axial velocity appeared around the centre of the liquid phase zone in the axial line of the radiator's face, and it did not increase linearly with the driving force increasing. Experiment results showed that a borderline in the area from the radiator's face to the boundary of the ingot formed by acoustic streaming. The solidification structure of one side of the borderline was absolutely different from the other's. The structures of the side under the radiator's face were all well refined by the duple action of cavitation and acoustic streaming, while the other side's were coarse and dendritic.