The Jominy end quench test has been adopted to investigate the effect of trace scandium on the quench sensitivity of Al-7Si-0.6 Mg alloys. The results show that at a lower quenching rate, the preferred precipitation of the Al3Sc phase inhibits the formation of a β′-Mg2Si phase, promoting the nucleation of finely dispersed metastable Mg2Si precipitates in the subsequent aging treatment. The quench sensitivity of the Al-7Si-0.6 Mg alloy was effectively improved by more than 60%. Rapid quenching rates can cause the Al matrix of the alloy to be in a supersaturated state, resulting in enhanced mechanical properties after aging treatment. In contrast, slow quenching rates precipitate the relatively coarse β′-Mg2Si phase and also produce a precipitate free zone during the quenching process, thereby diminishing the mechanical properties of the alloy after the aging treatment, so that the Al-7Si-0.6 Mg alloy possesses higher quench sensitivity.