Abstract: The production flowsheet for 012 ~ 32 mm bars of gear steel 20CrMo (/%:0.19 〜0.23C, 0.48 ~ 0.58Mn, 0.24 〜0.28Si, 0.009 -0.015P, 0.003〜0.012S, 0.87 ~1.08Cr, 0.17 ~0.18Mo, 0.024 ~ 0.046Als) is desulphurizing hot metal-120 t top and bottom combined blowing converter-LF-soft argon blowing-200 mm x 200 mm billet concasting-continuous rolling process. Results show that with using the process measures including controlling hot metal [S]≤0.030% , BOF end [C] 5:0.08% and end [P]≤0.012% , adding 0.6 ~ 1.0kg/t aluminium pig for pre-deoxidizing at BOF tapping, controlling LF refining slag basicity 3.5 〜5.0, casting liquid overheating extent 20 ~30 ℃, casting rate 1. 1 ~ 1. 4 m/min, beginning rolling at 1 060 ~ 1 100 °C and finishing rolling at ≤900 ℃，the total oxygen content and the nitrogen content in steel are respectively 12. 5 x 10^-6〜22. 5 x 10^-6 and 33 x 10^-6 ~40 x 10^-6, the rating of central and general porosity in rolled products is 0. 5 ~ 1. 0, the hot upset test and the mechanical properties of steel meet the requirement of standard, and the hardenability band width △J₉ HRC value is 3. 0 and the △J₁₅  HRC value is 4. 2.