Abstract: The heat treatment tests of 6005A aluminum alloy with different quenching methods（air cooling, air cooling,water cooling） were carried out. The microstructure of the alloy was observed by optical microscope, scanning electron microscope and transmission electron microscope. An electronic universal testing machine was used for the tensile test, and the optimum aging process in different cooling modes was obtained from aging-hardening curve of the alloy. The results show that the cooling mode has a certain effect on the strengthening and deformation mechanism of peak aging 6005A alloy. The peak hardness of T6 state 6005A alloy increases with the increase of quenching speed. Rapid cooling（water cooling） and medium speed cooling（air cooling） can precipitate β’ and β’ phases with high precipitation strengthening effect on aluminum alloy during artificial aging. The alloy obtained by rapid cooling（water cooling） has the highest strength. The plasticity of the alloy obtained by slow cooling（air cooling） is the best. High comprehensive mechanical properties can be obtained by medium speed cooling（air cooling）.