Abstract: By optimizing the composition design of 26CrMoVTiB steel for oil drilling casing,the steelmaking process of "BOF→LF→VD→CC" is adopted. Strictly control the slag discharge from the converter after steelmaking,leaving 3-5t of molten steel in the furnace after steelmaking. In the LF process,the amount of high-quality white ash used is 7-10 kg/t steel,the amount of refined slag used is 15-20 kg/t steel,the amount of silicon carbide used is 3. 0-5. 0 kg/t steel,the amount of aluminum particles used is 0. 5-0. 7 kg/t steel,and the flow rate of argon gas in the ladle is 300-600 L/min to ensure the stirring effect of the steel. Control ranges of LF refining slag composition are w（CaO） = 50%-55%,w（Al₂O₃） =26%-31%,w（SiO₂） ≤9%,w（MgO） ≤6%,w（TFe + MnO） ≤0. 5%. The constant pulling speed of φ450 mm section continuous casting billet is 0. 42 m/min,the stirring current is controlled at 150-300 A,the stirring frequency is 2. 0-8. 0 Hz,the superheat of the continuous casting ladle is controlled at 20-30 ℃,and the surface temperature of the billet is not higher than 180 ℃ when it exits the pit. The 26CrMoVTiB steel continuous casting billet for oil drilling casing with a diameter of φ450 mm can be produced with P mass fraction less than 0. 010% and S mass fraction less than 0. 001 5%. The segregation range of the continuous casting billet composition is as follows: w（C） ≤0. 03%,w（Mo） ≤0. 04%. This has ensured excellent corrosion resistance and wear resistance of the oil drilling casing steel,thereby extending its service life of the product.