Abstract: The hypoeutectic Al-8% Si alloy was prepared by using controlled diffusion solidification with forced convection mixing method.The effects of different precursor alloy composition and mixing temperature on the morphology and size of primary α-Al phase in the microstructure of hypoeutectic Al-8%Si alloy were investigated.The results show that the primary α-Al phase in Al-8%Si alloy prepared after mixing with pure Al and Al-12%Si alloy is a fine and round spherical crystal, and when the mixing temperature of pure Al is 665℃, the refining effect of the primary α-Al phase is the best, and the grain size can reach 43 μm.With the increase of Si content in the precursor alloy and the increase of mixing temperature of pure Al, the refining effect of the primary α-Al phase becomes worse.