The invention relates to a method for building the container bottom of a carbon-containing molten steel container, which comprises the following steps: firstly, pouring a high-aluminum pouring material layer 2 into a casing 1 of the molten steel container; building a carbon-free working layer 4 below a working layer 3 at the wall of the molten steel container and a carbon-containing working layer 5 above the working layer 3 at the wall of the molten steel container by three layers of carbon-free precast blocks 7; arranging the carbon-free precast blocks 7, a ventilation brick 8 and a slide water gap 9 at an impact area on the high-aluminum pouring material layer 2 at the container bottom 6 of the molten steel container; pouring a carbon-free pouring material layer 10 at a non-impact area on the high-aluminum pouring material layer 2 at the container bottom 6 of the molten steel container; and after pouring the container bottom 6 of the molten steel container, filling by a carbon-free pouring material along the carbon-free working layer 4 on the carbon-free pouring material layer 10 into a slope type encircling wall 11. The invention solves the change of physical properties, such as carbon-containing brick chalking, folding strength and the like, caused by the water of a pouring material at the container bottom of the molten steel container, controls steel clamping caused by the replacement of the bottom, has more stable running of the impact area at the bottom of a tank and is beneficial to the unity of large back molten steel containers with various varieties.