The invention discloses an automatic feeding technology for a large-sized flat ingot casting. The technology includes the steps that liquid-state premelting slag is added into a riser of the large-sized flat ingot casting; then at least three electrodes are inserted into the liquid-state premelting slag, two of the electrodes are graphite electrodes and another electrode is a consumable electrodebar which is made of the same material as that of the ingot casting; the graphite electrodes are powered up to heat a slag bath for feeding, and the consumable electrode bar can be fed in the feedingprocess. According to the automatic feeding technology for the large-sized flat ingot casting, the consumable electrode bar is added, the amount of molten steel reduced in the steel ingot feeding process can be provided through the electrodes, and meanwhile upper heat can be carried into the lower portion of a steel ingot through metal droplets in a dripping mode in time; the vertical axis direction temperature gradients can be effectively fused in the high-temperature mass transfer process, the temperature gradient within the range of 45-60 degrees is formed, the ingot casting solidificationcrystallization direction is changed thoroughly through the temperature gradient, the ingot center is loosened and moved upwards gradually and is finally moved into the riser, and meanwhile hole shrinkage is removed; and the automatic feeding technology has the characteristics of being simple, easy to control, good in effect and the like.