In order to determine the critical forging penetration efficiency(FPE)of 06Cr19Ni9NbN steel,a new model was presented to describe critical FPE,which is significant to optimize the steel forging process.The plane strain compression tests were conducted to obtain the model and confirm its validity.The results indicated that the dynamic recrystallization(DRX)volume fraction increases and the grain size decreases with the rise of reduction ratio.Meanwhile,the compression process was simulated by DEFORM software.The tensile tests were conducted and the results demonstrated that the mechanical properties gradually become stable when the reduction ratio increases to 30%,34% and 40%at 1 200,1 100 and 1 000°C,respectively.The calculated results based on this new model are consistent with experimental results,indicating that the model is suitable to predict the critical FPE for the steel. In order to determine the critical forging penetration efficiency (FPE) of 06Cr19Ni9NbN steel, a new model was presented to describe the critical for FPE, which is significant to optimize the steel forging process. The plane strain compression tests were conducted to obtain the model and confirm its validity. These results indicated that the dynamic recrystallization (DRX) volume fraction increases and the grain size decreases with the rise of reduction ratio. Meanwhile, the compression process was simulated by DEFORM software. The tensile tests were conducted and the results results that the the mechanical when the reduction ratio increases to 30%, 34% and 40% at 1 200,1 100 and 1 000 ° C, respectively. The calculated results based on this new model are consistent with the experimental results, indicating that the model is suitable to predict the critical FPE for the steel.