A study has been performed on the effect of Thermomechanical Treatment on the toughness of 7075 Aluminum alloy. Three different heat treatments such as Intermediate Thermomechanical Treatment (ITMT), Thermomechanical Treatment (TMT-2) and Conventional Heat Treatment have been applied in this study. The experimental results showed that the ductility and the toughness were increased by ITMT and TMT-2 compared with Conventional Heat Treatment, It was believed that the increase of ductility was due to grain size refinement, and that the toughness increased was due to grain size refinement, retardation of the recrystallization and homogeneous distribution of small Cr-rich particles.