Abstract: Thermal analysis technology and high temperature quenching technology were used to research Al-7%Si alloy′s solidification process. The characteristic parameters such as TC, ΔTC, ΔtC were introduced to show the primary phase′s precipitation, and Tm, Te, ΔTe, θ and Δte were introduced to show eutectic phase′s formation. The results show that, microstructure evolution of Al-7%Si alloy during solidification could be well reflected by characteristic parameters at cooling curve. With the increase of cooling speed, the super-cooling degree of primary phase′s nucleation ΔTC and primary phase′s solidification time ΔtC decreased, that is to say, the primary phase′s nucleation rate increased and its growth was disturbed. Meanwhile, the super-cooling degree of eutectic phase′s ΔTe increased and eutectic phase′s solidification time ΔtC decreased, the growth of eutectic phase was prohibited. But the cooling speed had no significant effect on eutectic phase′s nucleation temperature Tm, that is to say, increasing cooling speed could not increase eutectic nucleation ratio.