The invention discloses a vacuum negative-pressure casting process capable of ensuring the casting quality of a roll collar, belongs to the technical field of vacuum negative-pressure casting, and is applicable to improvement on the casting quality of the roll collar of a furnace bottom roll of a steel rolling heating furnace. According to the technical scheme, an EPS (expandable polystyrene) foam plastic model is wrapped with waste-based bauxite model coating; the EPS foam plastic model buried in dry sand is burnt off before molten steel is poured, so that a solid mold is changed into a hollow coating shell; carbon elements in a solid mold model are prevented from entering a casting body in the pouring process and then the pouring of the molten steel is completed, so that the problem of recarburization on a low-carbon casting, caused by the EPS foam plastic model, is thoroughly solved, and the defects of pore forming, impurity carrying and the like of the casting are greatly reduced. By using the vacuum negative-pressure casting process, the quality is high, the efficiency is high, the cost is low, the operation is easy, the quality of a casting product is improved, the problems existing in a vacuum negative-pressure solid mold casting technology for a long time are solved, and the process is a new method for producing a high-additional-value alloy casting, has a giant business value, and is worthy of popularization and application in the industry.