Mechanical vibration was applied to the solidification of a lost foam cast (LFC) 356 aluminum alloy.Effects of mechanical vibration, with different peak acceleration, on the size and morphology of α-Al phase, and also on the mechanical properties of the castings were studied. Results indicated that α-Al dendrites gradually grow into equiaxed grains as the peak acceleration of vibration is increased. When the peak acceleration is between about 1 to 4 g, α-Al phase distribution is uniform and is refined obviously, α-Al dendrites are reduced and the mechanical properties of the castings are improved significantly when compared to those of the castings that are produced without vibration. However, when the peak acceleration is higher than 4 g, strong vibration will lead to defects formation, such as sand adhesion, while the amount and size of pores will be increased. And due to the turbulent flow that caused by strong vibration, the chance of forming large pores in the matrix has been increased significantly. The increase in defects will result in the deterioration of mechanical properties.