Dynamic mechanical behaviors of high strength reinforcing steel bar HRB500 were experimentally studied over the range of strain rates from 49s-1 to 590s-1. Dynamic constitutive models based on characteristic values of mechanical performance and Johnson Cook(J C) model were proposed to describe the dynamic mechanical behaviors of steel bar HRB500. It is found that the mechanical behavior of steel bar HRB500 is strain rate dependent. The yield strength, the ultimate strength as well as the strain corresponding to the ultimate strength increase as the strain rate increases. The dynamic increase factor for yield strength is more appreciable than that for ultimate strength at the same strain rate. However, the strain rate sensitivity of steel bar HRB500 is slightly weak in comparison with those of low strength steel bars, such as HPB235, HRB335 and HRB400. It is suggested that dynamic constitutive model based on characteristic values of mechanical performance can be used to describe the dynamic mechanical behaviors of steel bar HRB500 over the range of strain rates from 30×10-4s-1 to 500s-1, and the dynamic constitutive model based on J C model can be used to describe the dynamic mechanical behaviors of steel bar HRB500 over the range of strain rates from 10s-1 to 500s-1.