The Al-Si eutectic alloy solidified under normal pressure was prepared by vacuum Ar-arc furnace. The alloy solidified under high pressure was prepared by hexahedral anvil equipment. The two heavily etched samples were observed by scanning electron microscope. The experiments show that the eutectic silicon phase solidified under high pressure presents curved and near parallel lamellar crystal, and there is definite spacing between the layers, which was very different from that of solidified under normal pressure. So the eutectic growth mode of Al-Si alloy solidified under high pressure was put forward, which indicate that the growth mode of Si have been changed gradually from facet to non-facet under high pressure.