Abstract: The hot compression experiment of Al-1.1Mn-0.3Mg-0.25RE alloy was done on Gleeble 1500 thermo simulation test machine. The thermo deformation behavior was studied at 300-500 ℃ and the strain rate of 0.01-10 s-1. On this basis the constitutive equations and the processing map were obtained. The results show that the steady flow stress could be described by the hyperbolic sine constitutive relation, the hot deformation activation energy was 186.481 7 kJ ·mol-1, and the material constants of A, α and n were 1.076 97×1010 s-1, 0.037 403 and 5.875 667 respectively. The optimum deformation temperature of the alloy was 450 ℃ and the optimum strain rate was 0.01 s-1.