Abstract: Isothermal compression tests for a new Al-Mn alloy were carried out at the strain rate range of 0.01-10 s-1 and at temperature of 350-550 ℃ on Gleeble-3500 thermal simulation system, and the flow stress behavior during hot compression was studied. The thermal processing map was obtained by dynamic material model(DMM), and the relations between microstructure and deformation temperature and strain rate were studied. The results show that the hot compression flow stress behavior of the tested alloy could be described by the hyperbolic-sine equation with the average activation energy of 194.757 kJ·mol-1. The optimum temperature and strain rate of the tested alloy, which were got by combining thermal processing map and microstructure, were 500-550 ℃ and 0.1 s-1, respectively. The subgrains were elongated deformed microstructure at high Z value and some well-formed subgrains with low density dislocations were formed at low Z value.