Abstract: Al-Mg-Si alloys are widely used in electronic communication, heat dissipation and power transmission because of their excellent thermal and electrical conductivity. However, a synergistic improvement in the strength and conductivity is challenging because their paradoxical relationship. Based on the alloy design of high mechanical properties, the influence of different Mg/Si ratios on the strength and thermal or electrical conductivity of the alloy was investigated, and the experimental results were analyzed theoretically by DSC analysis and JMatPro simulation. The results show that the hardness and strength decrease with increasing Mg/Si ratio for a certain Mg content, while the electrical/thermal conductivity shows an opposite trend. The properties change of the alloys is related to the precipitation kinetics of the main strengthening phases β’. The precipitation rate of β’ is much higher in low Mg/Si ratio alloys than the alloys with high Mg/Si ratio during aging. More adequate precipitation occurs in the alloy with a Mg/Si ratio of 1.02, which is close to the Mg/Si atomic ratio of β". Therefore,the alloy with 1.02 Mg/Si ratio exhibits relatively better performance under the same aging conditions.