In order to research the mechanic performance of 7A05 aluminum alloy, a series of tests, including tensile test about aluminum alloy substrate, tensile test about aluminum alloy butt welded joint, tensile test about transverse partition of aluminum alloy welded joint and hardness test were conducted. The results of these tests indicate that the strength and hardness of HAZ of this material exhibit a W-shaped reduction. There are an symmetrical softened area at 10~20mm from the center of weld. Due to ageing effect, the strength and hardness of HAZ can resume to 80%of the substrate one month after welding. Based on the analytical deduction and experimental data fitting, the theoretical strength model for HAZ of aluminum alloy is proposed. For the purpose of engineering design, the HAZ is transformed into a uniform strength reduction zone, the width and strength value is determined according to the principle of equal strength.