Abstract: By using micro-Vickers hardness test, uniaxial tensile, and microstructure characterization by scanning electron microscope (SEM) and transmission electron microscope (TEM), the effects of heat treatment process on the microstructure and mechanical properties of Al-Mg-Si-Sc-Zr alloy were studied. The results show that the long strip Mg₂Si with a mesh distribution at the grain boundary transforms to granular Mg₂Si with the increase of hold time during solution treatment (575 ℃). As for Al₃(Sc, Zr) particle, the optimized high-temperature aging treatment is 320 ℃×1 h. A large amount of nano-sized Al₃ (Sc, Zr) particles can be observed in 320 ℃×1 h treated alloy, which could significantly strengthen the matrix. As for aging induced precipitates, the aging precipitated phase changes from GP zone to β" phase with the increasing low-temperature aging temperature. The heat treatment process showing the best comprehensive mechanical properties in the uniaxial tensile test is 575 ℃×0.5 h+320 ℃×1 h+120 ℃×46 h, and the corresponding yield strength, tensile strength and elongation are 197.8 MPa, 288.2 MPa and 13.3%, respectively.