Abstract: The Al–6%Si (mass fraction) semi-solid billets were prepared by liquid phase reaction sintering in this paper, using Al and Si elemental powders. In the results, the mixed Al–6%Si powders have the good cold pressing forming properties, and the relative density can reach 97.6% after 500 MPa cold pressing. The cold pressing characteristics of the mixed powders can be described by Huang Pei-yuan pressing equation. The Al and Si elemental powders can react to form the liquid phase at 585 ℃, which forms a semi-solid microstructure around the equiaxed solid phase Al grains. At the same time, the Al grain size and the liquid phase content of Al increase with the increase of reaction time. The reaction sintering of Al–6%Si elemental powders is a reaction sintering system with the continuous liquid phase, and the microstructure of the semi-solid billet can be controlled by controlling the reaction time.