The invention discloses a method for reducing B inclusions in aluminium-free deoxidized steel. The method comprises the following steps: 1) converter steelmaking: overoxidation tapping is avoided; deoxidation alloying is performed by adopting low-aluminium SiBaCa, ferrosilicon and mid-carbon ferromanganese during tapping, lime and fluorite are added, and silicon content of molten steel is controlled to be 0.55wt%-0.65wt%; (2) LF (ladle furnace) refining: lime and fluorite are added in batches in heating slagging of the LF, and final slag basicity is controlled to be 2.0-3.0; silicon content ofmolten steel is controlled to be 0.60wt%-0.70wt%, and vacuum treatment starts after soft blowing with argon at rate of 80-200 L/min for 10-20 min; 3) RH furnace refining: an RH furnace is kept at ultimate vacuum degree for 15-25 min and subjected to vacuum killing, then argon flow is regulated to 150-250 L/min, argon is blown for 1-3 min, then the argon flow is regulated to 80-200 L/min, soft blowing is performed for 8-15 min, and a product is discharged from the furnace and loaded to a casting machine. Over-standard rate of the B inclusions in steel products is reduced by process improvement.