Superplastic deformation behavior of materials is generally affected by the microstructural change during the deformation. The grain size changes due to the recrystallization and grain growth during high temperature deformation and is known as the most important structural factor affecting superplasticity. The characteristics on grain growth and recrystallization of 8090 Al-Li alloy at high temperature were investigated. The microstructural change of 8090 Al-Li alloy during isothermal annealing and during tensile deformation at 450℃ 500℃, 530℃ were observed. The static grain growth was observed without recrystallization during isothermal annealing, while both the strain-enhanced grain growth, which is faster than static grain growth, and the dynamic recrystallization were observed simultaneously during tensile deformation. The effects of strain and strain rate on strain-enhanced grain growth and dynamic recrystallization were analysed. The high strain rate is effective in developing a fine recrystallized microstructure which is suitable for superplastic deformation. The critical strain for the dynamic recrystallization is about 0.35-0.4. The two-stage strain rate tension test was conducted in order to enhance the elongation-to-failure of superplastic 8090 Al-Li alloy by maintaining the grain size as fine as possible through the control of grain growth and recrystallization during the deformation. And the instability parameter was considered to avoid the fracture due to necking in determining the strain where the strain rate changed. The optimum strain rate during deformation is $3×10^{-3}sec^{-1}$ to the strain of 1.18 for the first stage deformation and $3×10^{-4}sec^{-1}$ for the second stage deformation.
