The invention relates to a preparation method of a reactive sintered boron carbide-silicon carbide composite ceramic material. The preparation method comprises the following steps: (1) mixing: ball milling raw materials (80-90wt% of boron carbide, 5-18wt% of carbon dust and 1-5wt% of a sintering aid) in a ball milling tank; (2) molding: putting the mixture obtained in the step (1) in a mold and performing dry pressing molding to obtain a boron carbide ceramic biscuit; (3) reactive sintering: putting the boron carbide ceramic biscuit obtained in the step (2) in a reactive sintering furnace; sintering at a high temperature in vacuum for infiltrating and melting a metal silicon wafer to obtain the reactive sintered boron carbide-silicon carbide composite ceramic material. The method disclosed by the invention, raw materials and proportion are scientific and reasonable; the production method is safe and low in cost; the prepared boron carbide-silicon carbide composite ceramic material is capable of meeting the thermal neutron shielding performance requirement for waste in the nuclear industry.