Abstract: The Lagrangian analysis method is employed in the present paper to investigate the dynamic constitutive relationship and equation of state for rock salt under impact compression and combined pressure shear impact loading. The results show that the stress-strain relationship is evidently non-linear and rate-dependent .Based on P-V Hugoniot curves, the sample is skown to be a porous material with void volume about 3 percent. With flaws in the meso scale, rock salt sample melts around these flaws during impact loading, and the transversal form of shear wave is greatly changed. Therefore, no further discussions on shear behaviors are conducted. In the process, the flaws seem to be recovered after melting.