Abstract: The dynamic recrystallization and flow stress mcxlels of Q235 (plain carbon steel) were established by regression with experiment data, and the flow stress model was used for work hardening zone,the results calculated by the models agreed with those measured results. The condition of upsetting test was:temperature,900~1150℃ forming rate,0.01~1.0s^-1; initial grain size,48~85 μm.