Abstract: The effects of multi-stage homogenization on the microstructures and ultimate mechanical properties of aluminum alloy 7055 were studied by optical microscopy, scanning electron microscopy, EDS and tensile test using intermediate frequency furnace smelting of aluminum alloy 7055. The results show that aluminum alloy 7055 ingots with no multi-stage homogenization treatment exists serious dendritic segregation. After 30 h single stage homogenization treatment at 470 ℃, the non-equilibrium phase on the grain boundaries decreases by forming discontinuous distribution and composition segregation improvement. The homogenization improves and the number of non-equilibrium phase increases with additional intermediate insulation at 410 ℃ for 4 h. The grain boundary shape is more regular. The third stage homogenization treatment, which is composed of isothermal heating at 250 ℃ for 4 h, then heated to 410 ℃ for 4 h and 470 ℃ for 30 h, greatly eliminates the non-equilibrium solidified eutectic on the grain boundaries. The mechanical properties are the best after aging.