Liquid impact forming (LIF) is a new type of composite forming technology developed on the basis of hydraulic bulging and stamping. When the upper and lower dies move towards the radial direction of the thin-walled tube, it generates internal pressure to quickly fill the mold cavity and complete the bulging process. LIF is expected to improve the forming efficiency and properties of metal thin-walled tubes, and the high-precision plastic hardening model not only has an important influence on the analysis of the forming mechanism, but also has an important prerequisite for finite element numerical simulation. In this paper, the basic theory of constitutive relationship and strain rate response of materials were analyzed, the dynamic plastic hardening model was proposed and derived from the J-C constitutive model, which is based on the mechanical condition under liquid impact forming according to the tube stress conditions. The dynamic plastic hardening models obtained from liquid impact forming were taken as the material parameters by finite element simulation, and then by comparing with the experimental results, the precision of dynamic plastic hardening model was verified.