The tapping hole of converter is a refractory material channel of converter. When tapping, molten steel is injected into the ladle through the tapping hole. When the tap hole brick is partially damaged, molten steel passes through the tap hole brick to reach the furnace shell area, and the furnace shell steel plate at the joint of flange plate and furnace shell is penetrated, so that slag and steel flow out. After steel piercing, it is necessary to add the remaining molten steel into a large quantity of lime to adjust slag, and then pour the remaining molten steel into the ladle from the large furnace mouth to prevent large area burning of the furnace shell. Due to the lack of slag blocking measures for tapping at large furnace mouth, the slag and steel are discharged together, and the slag and phosphorus return are serious, which is easy to lead to the phenomenon of high phosphorus in finished products and furnace mouth burning.