In order to study the dynamic mechanical properties of 2219 aluminum alloy, dynamic compression experiments were carried out through split Hopkinson impact pressure bar (SHPB) equipment on 2219 aluminum alloy in two heat treatment states (T4 and T6). The microstructure of the obtained samples is analyzed by OM and XRD. It is found that the flow stress of the material decreases significantly when the strain rate exceeds 2000 s-1 under the two heat treatment conditions, that is, a significant strain rate softening behavior occurs. Based on the two-dimensional contour map of strain rate sensitivity behavior with real strain and strain rate, it is found that the material exhibits negative strain rate sensitivity behavior under the condition of high strain and high strain rate, and the flow stress decreases with the increase of strain and strain rate. Through theoretical calculation and microstructure characterization, it is found that the softening effect caused by temperature rise softening and lamellar grain breakage is an important reason for the negative strain rate sensitivity behavior of the material at a high strain rate and high strain rate.