The effects of solution and aging treatments on the microstructures and mechanical properties of 7055 Al alloy bars were studied by transmission electron microscopy, optical microscopy and tensile mechanical property testing. The results show that an appropriate combination of solution and aging treatments plays an important role in controlling microstructure so as to obtain improved mechanical properties. Two-step solution of 470 oC/20 min+480~490 oC/20 min could further decrease the amount of undissolved particles and is helpful to enhance age-strengthening. When the 2nd-step solution temperature is increased to 490 oC, the volume fraction of undissolved particles decreases remarkably, from 2.5% in the case of one-step solution treatment to 2.0%. The grain size of the as-solutioned alloys under experimental conditions is in the range of 30~35 μm. Optimum combined mechanical properties are achieved under the regime of 470 oC/20 min+485 oC/20 min solution- treatment followed by 135 oC/16 h + 190 oC/10 min aging treatment, with the tensile strength and yield strength being 694 MPa and 660 MPa, respectively, in the meantime maintaining a high elongation to failure of 14%