The invention discloses a method for introducing a silicon carbide-based synthetic material to improve slag resistance of an ultralow carbon-magnesium-carbon material and belongs to the technical field of preparation of refractory materials for ferrous metallurgy. The method comprises the following steps: sufficiently and uniformly mixing a SiO2-based natural ore with waste slag and a carbon source, putting into a high-temperature furnace, and preparing a SiC-based synthetic material in an inert gas atmosphere; sufficiently mixing the SiC-based synthetic material with an ultralow carbon-magnesium material according to a certain ratio, and carrying out molding, drying and high-temperature thermal treatment, thereby obtaining the silicon carbide-based synthetic material improved ultralow carbon-magnesium-carbon material; finally carrying out a slag resistance experiment by using a static crucible method. By adopting the method, on premise that the content of carbon of a MgO-C material isreduced, the slag resistance of the ultralow silicon carbide-based synthetic material is improved, and quality requirements of steel refining and continuous casting processes on related refractory material components can be met. The method is simple and feasible in process, low in raw material price, easy in raw material obtaining and easy in large-scale production.