The invention relates to a SiC-Si3N4 high temperature ceramic furnace bottom plate for an annular furnace and a preparation method thereof; the preparation method comprises the following steps: on a basis of a total weight part of 100 parts, weighing 25-75 parts of Si powder and the balance of SiC powder; adding 3-8 parts of a sintering aid and 4-9 parts of a binder, wherein the sintering aid is Y2O3, or a mixture of Y2O3 and Al2O3; performing material mixing, molding, sintering, silicon immersion, and machining to prepare the SiC-Si3N4 high temperature ceramic furnace bottom plate for an annular furnace. The preparation method is simple in process and low in cost, and the obtained product has the characteristics of high temperature resistance, good creep resistance, large high-temperature strength, good thermal shock resistance, and the like, can meet working condition requirements for annular furnace production, and can effectively solve the problems of poor high temperature resistance of metal furnace bottom plates, furnace bottom plate bending deformation due to a large material high-temperature creep rate, furnace bottom plate cracking damage due to a large material thermal expansion rate, and low service life.