The invention discloses a preparation method of a high-density silicon carbide ceramic composite material. The preparation method comprises the following steps of: S1, putting silicon carbide powder,carbon black, boron nitride nanosheets and a combustion assistant into a grinder, carrying out wet ball-milling mixing, drying, and screening to obtain mixed powder; S2, carrying out compression molding on the mixed powder by adopting a cold isostatic pressing molding process to obtain a biscuit; S3, performing pressureless vacuum sintering on the biscuit so as to obtain a presintered body; and S4, performing spark plasma sintering on the presintered body to obtain the silicon carbide ceramic composite material. According to the preparation method, wet ball-milling mixing is performed on the raw materials in a reasonable ratio to obtain the mixed powder; compression molding is performed on the mixed powder by adopting the cold isostatic pressing process to obtain the biscuit with relatively high density; and the biscuit issintered through a pressureless sintering and spark plasma sintering combined manner; and therefore, the preparation of the high-density, high-hardness and high-strength silicon carbide ceramic composite material is realized. The method is simple in process and convenient for industrial production.