The 6××× series aluminum alloys Al-Mg-Si-Cu are widely used in the transportation and building industries due to their comprehensive mechanical properties, adequate formability, high corrosion resistance and good weldability. For decades, ultrafine grain structure (UFG) produced by severe plastic deformation (SPD) has been proved to be a promising way in strengthening Al alloy materials. Although this method can guarantee a great improvement in strength, the obtained ductility is always disappointing. Besides, this method has a limitation to fabricate products suitable for practical use. Recently, combining deformation and aging has been proposed to produce high-strength Al alloys. This strategy is very effective in achieving Al alloys with strength-ductility synergy even through conventional producing process, for example, rolling and aging. The strain ratio of deformation is critical in tuning the mechanical properties which could be acquired by the above method. The effect of deformation strain ratio on the age-hardening behaviors and microstructure in Al-Mg-Si-Cu alloy produced by combining cold-rolling and aging are investigated using hardness test, tensile test, EBSD and TEM in this work. The results show that the as-rolled hardness increases gradually with deformation strain ratio. The age-hardening potential declines with the increase of strain ratio, though post-aging could further strengthen the as-rolled alloys. The grains elongate along the rolling direction during deformation and finally have a lamellar structure. Fragmentation and extensive defects like sub-grain boundaries occurs inside the grains. The dislocations become denser inside the alloy with the increase of the deformation ratio. When the deformation ratio is large (above 60%), formation of dislocation tangling and sub-grains are observed. Deformation-induced change of the dislocation configuration affects the precipitation significantly. Due to the interaction between solutes precipitation and defects annihilation, the distribution of precipitates undergoes a change from being isolated to a continuous manner.