Abstract: Al-8.8Zn-1.4Mg-0.5Cu-0.1Sc-0.1Er-0.1Zr alloy was subjected to isothermal compression tests on Gleeble 3800 thermal simulation testing machine under conditions of deformation temperature of 380-440℃, strain rate of 0.01-10 s^-1 and deformation amount of 45%, 60%. The hot deformation behavior of the alloy was studied, and the deformation constitutive equation and hot processing map based on dynamic material model were established. The best range of hot processing parameters was confirmed, and the microstructure of characteristic zone was observed. The results show that test alloy showed characteristics of isothermal rheological, sensitivity of positive strain rate and negative temperature. The best range of hot processing parameters within test range was deformation temperature of 425-440℃ and strain rate of 0.01-0.02 s^-1. The instability zone of the alloy mainly appeared in the condition of large strain, low deformation temperature and large deformation amount. The dislocation pile-up and adiabatic shear band in the microstructure were main reasons for the instability of test alloy.