The invention belongs to the field of 
metallurgy, and relates to a cast steel riser covering agent as well as a preparation and using method thereof. The cast steel riser covering agent comprises thefollowing components of, with the total 
mass units being 100 parts, 15-40 parts of 
aluminum electrolysis waste 
cathode carbon block, 10-35 parts of 
dolomite, 10-25 parts of 
vermiculite, and 20-40 parts of 
aluminum electrolysis waste 
silicon carbide-
silicon nitride bricks. During preparing, firstly, crushing and 
grinding the dried raw materials, wherein the particle size is not more than 2 mm; weighing the raw materials according to the composition quality of the raw materials, uniformly stirring, and 
drying to obtain the cast steel riser covering agent. During using, a steel 
ladle is added into the cast steel riser covering agent to form a 
slag layer, so that the thickness of the 
slag layer is 6-8 cm, the liquid surface of the steel 
ladle does not leak red, and the 
slag layer is not crusted. By using the cast steel riser covering agent, the heat loss at the top of the riser can be solved, the solidification speed of 
molten steel in the riser can be prolonged, the feeding capacity of the 
molten steel in the riser is improved, the process yield of the 
casting is guaranteed, the height of the riser is reduced, the 
molten steel is saved, and finally the cost is reduced.