The non-equilibrium microstructures of hyper-eutectic Al-26.6wt%Si solidified under superhigh pressure (5.5 GPa) have been investigated. The results show that there exists a great deal of primary alpha phase in hyper-eutectic Al-Si alloy. The non-equilibrium microstructure for hyper-eutectic Al-Si alloy is composed of primary alpha phase, beta phase and (alpha + beta) eutectic phase. The solid solubility of Si in alpha phase and the solid solubility of Al in beta phase increase significantly. The effects of high pressure on the solidification structures of Al-Si alloy are discussed.