Isothermal compression tests of 4045 aluminum alloy were carried out at the strain rate range of 0.01~10 s-1 and at the temperature range of 300~450 ℃ on Gleeble-3500 system to study the hot deformation behavior and hot workability. The results show that the flow behavior of 4045 aluminum alloy can be described by the hyperbolic-sine equation with the average activation energy of 189.93 kJ/mol. The processing maps were calculated on the basis of the dynamic materials model (DMM).The optimum processing parameters were obtained at strain rate range of around 0.1~0.3 s-1 and deformation temperature range between 380 °C and 450 °C on the basis of processing map and microstructural evolution analysis.