Abstract: A new type of Al-Mg-Si-Cu aluminum alloy was designed, and the alloy composition was Al-0.42Mg-0.50Si-0.99Cu. The effects of different aging treatments on microstructure, mechanical properties and corrosion behavior were studied by optical microscopy, transmission electron microscopy and means of conventional tensile test. The results show that no distinct grain boundary precipitates were observed in T6 under-aging state and the grain boundary precipitates are small and continuously distributed in T6 peak-aging state, and intergranular corrosion was serious. With the increase of aging time, Q′ phase increased and coarsened, the grain boundary precipitates were coarsened obviously and sparsely distributed. In double aging state, there are plenty of Q′ precipitates in matrix, grain boundaries precipitates were spheroidization, the spacing between precipitated phases increased, precipitated phaseand were continuously distributed and the PFZ was broaden. In T6 peak-aging state, the alloy had the most serious intergranular corrosion tendency and had the highest strength, however, the corrosion resistance was obviously improved while tensile strength was a little decrease in double aging state.