The invention discloses a method for measuring the large ladle pouring allowance in the continuous casting pouring process. The method comprises the steps that (1) molten steel in N steel ladles of the same model is poured into a slag tank and naturally cooled till the upper-layer solidification thickness of the molten steel in the slag tank is larger than or equal to 30 cm; (2) the slag tank is transferred to a slag field and impacts with a cast iron column after being lifted, and thus steel slag is all poured into a special area of the slag field; (3) the steel slag is subjected to all-around artificial water injecting cooling in a water-cooled mode and then naturally cooled; (4) the water-cooled steel slag is crushed into steel blocks and block-shaped slag with the edge length being smaller than or equal to 300 mm, and the steel blocks and the block-shaped slag are subjected to all-around artificial water injecting cooling and then naturally cooled for 2.0-4.0 h; and (5) after moisture in the steel blocks and the block-shaped slag is air dried, the broken steel blocks in the steel slag are attracted through lifting magnets, the mass of the steel blocks is the total amount of remaining steel in the slag tank, and the average pouring allowance is equal to the mass of the steel blocks/N, wherein the average pouring allowance is the remaining steel amount in the single steel ladle. The accurate method for measuring the large ladle pouring allowance is provided for a novel process for controlling roughing slag through annular steel outlet argon-blowing.