The effect of solid solution temperature on the age-hardening behavior and microstructure of Al-Mg-Si-Sn alloy was investigated using Vickers microhardness tester and transmission electron microscopy(TEM). The results show that increasing the solid solution treatment(ST) temperature from 560 ℃ to 590 ℃(enhanced solid solution temperature) significantly retards the natural aging(NA) of Al-Mg-Si-Sn alloy. After solid solution treatment and quenching, the time to peak hardness of natural aging is delayed from 3 d to 13 d. However, enhanced solid solution treatment does not significantly change the size of the precipitates of the peak aging state and the peak hardness of the artificially aged(AA) samples; the Sn-vacancy complex with a vacancy/Sn ratio greater than 1 is more stable, indicating that the enhanced solid solution treatment promotes the binding of Sn element to the vacancies through the simultaneous increase in the concentration of vacancies and the solubility of Sn, and thus retards the formation of natural aging clusters; the strengthening precipitates in artificial aging state are mainly β"/β' composite precipitates formed by heterogeneous nucleation on Sn-containing clusters; since the enhanced solid solution treatment can only slightly increase the solubility of Sn, its effect on the peak aging precipitation is very small; the different mechanisms of the Sn element lead to the different effects of enhanced solid solution treatment on natural aging and artificial aging.