Abstract: Elaborated here in the paper is the development process of the manufacturing technology for the Φ310 mm 12Cr5MoNT alloy steel CC round. The process technological routing i. e. 100 t UHP EAF→LF→VD→CCM→slow cooling is employed,and at the EAF melting stage,the C and P contents in the tapping steel is strictly controlled to the ranges,i.e.,C:0.03%~0.06%;P:≤0.010%,and the tapping temperature is ensured to be within the range of 1 650~1 670 ℃. For the refining process,the hi-alkalinity reducing slag system is adapted,and coping with the strengthening deoxidation process,the hi-vacuum duration is kept as ≥12 min for VD treatment,and the soft blow time is ≥25 min a bid to enhance the cleanness of the liquid steel.And for the CC process,the over temperature is control within 16~25 ℃,the constant drawing speed is kept at 0.75 m/min,and the whole-course shielding casing operation is implemented,and so is the double electromagnetic stirring in the mold and at the solidification end. Relevant practice shows that the above mentioned technological solution has brought about such advantages as obvious reduction of the chemical composition fluctuation range of the billet,proper control of the inclusions in the steel,and homogeneous and compact macro-structure,which is completely satisfactory to the quality requirement by the follow-up piercing process.