Abstract: In the FEM analysis of structure response under dynamic loading such as high velocity impact, the failure parameter is a important aspect of material behavior. With split Hopkinson tension bar tests and static material test at various stress states and temperatures, the effects of high strain rate, elevated temperature and stress triaxiality on the fracture behavior of 45 steel were studied. The Johnson-Cook damage fracture model parameters were exprimentally determined. The parameters were validated by comparison between the Taylor experiments and the simulations. The consistency between the experimental observation and numerical simulation indicates that the obtained parameters can describe the failure behavior of 45 steel under high speed deformation.