Abstract: The constitutive relation of an Mg-Al Alloy under uniaxial compression at high strain rates is fitted and checked using the SHPB(Split Hopkinson Pressure Bar)experimental results and the numerical simulation based on the fitted constitutive law of the specimen.Using the constitutive relation of the Mg-Al Alloy determined by quasi-static and dynamic compression tests in the one-dimensional simulation of the SHPB test,the reflected and transmitted pulses of SHPB tests can be reproduced.Furthermore,the stress,strain and strain rate of the Mg-Al Alloy obtained in the SHPB test are consistent with those estimated by the classical SHPB analyses.However,it should be noted that the strain rate of the specimen is not constant during SHPB test.