The hot deformation behavior of Cu-6 wt.% Ag alloy was described by hot compression tests in the temperature range of 973～1123K and stain rates of 0.01～10s_-1. The microstructure evolution of the alloy was investigated in this paper. The true stress-strain curves were studied to reveal the hot deformation mechanism of Cu-6 wt.% Ag alloy. A simple constitutive model was established. The Arrhenius equation and Z were quoted in this investigation to modified the model. The results show that the dynamic recovery, dynamic recrystallization occurred in Cu-6 wt.% Ag alloy during hot deformation. And twinning behavior was observed at the strain rates of 0.1s_-1 and 1s_-1 temperature of 1123K. This twining behavior result in sharp changing of flow stress. With the increase of flow stress, a valley of stress was observed directly. The modified model which integrated the influence of temperature, strain rates, strain on flow characteristic could predict the stress accurately and be compiled easily.