The invention discloses a method for preventing carbon-containing fireproof material from slag erosion. Through providing a suitable external voltage for a slag system, the penetration depth f the slag in a fireproof material is delayed, and the physical protection of the fireproof material is realized. The method includes steps of taking aluminum oxide, silica, and calcium oxide as raw materials, and preparing to be the slag powder with alkalinity of 0.8-2.3; heating the mixed powder to 1550-1650 DEG C to melt down; after decarbonization, contacting the carbon-containing fireproof material with slag, and then connecting the fireproof material after decarbonizing treatment and the slag to both electrodes of the power source respectively; electrifying at 0-4V; realizing the protection of carbon-containing fireproof material from slag erosion. The method can effectively inhibit the physical penetration of slag in the carbon-containing fireproof material, significantly improve the slag erosion resistance of the carbon-containing fireproof material, and prolong 3-4 times of the service life of the carbon-containing fireproof material. The method is simple in operation, wide in applicable slag scale, and high in production practical value.