The invention discloses a method for splashing slag of converter for protecting furnace. The method comprises the following steps: (1) determining the slag oxygen potential E by a sublance TSO probe before tapping, and calculating the FeO content W of the slag according to the regression formula; (2) calculating the slag volume, controlling the FeO content to 10-15% according to the splashing slag and calculating the dosage of a slag modifier to be added; (3) adding the slag modifier after splashing the slag for 30-40 seconds; in the slag modifier, the weight percentage of MgO is 50%wt, the weight percentage of CaO is less than or equal to 10%wt, the weight percentage of SiO is less than or equal to 6%wt, and the weight percentage of C is less than or equal to 10%wt. The content of FeO in the melting end-point slag is obtained according to the slag oxygen potential data and the fractional melting characteristic of the splashing layer is controlled by adjusting the content of FeO in the slag, so that the fractional melting amount of the splashing layer is reduced and the protective effect of the furnace lining by the splashing layer is increased.