The invention provides a medium of a high-voltage ceramic capacitor with high performance and middle-low temperature sintering, which relates to the technical field of inorganic non-metal material. The invention adopts the prior method for preparing the medium of the high-voltage ceramic capacitor to prepare the medium of the high-voltage high-stability ceramic capacitor containing no lead, cadmium or other toxicities, and having high performance and middle-low temperature sintering (the sintering temperature is between 1,100 and 1,150 DEG C) by the prior chemical raw materials of capacitor ceramics. The medium is applicable to the preparation of single-chip ceramic capacitor and multi-layer tablet ceramic capacitor so as to greatly reduce the cost for the ceramic capacitor and avoid environmental pollution during preparation and application. The medium is characterized in that the medium comprises the following compositions (in weight percentage): 58 to 92 percent of BaTiO3, 2 to 19 percent of SrTiO3, 0.5 to 10 percent of CaZrO3, 0.05 to 1 percent of Nb2O5, 0.03 to 1.0 percent of Y2O3, 0.03 to 1.0 percent of Co2O3, and 6 to 30 percent of Bi2Sn2O7, wherein each of the BaTiO3, the SrTiO3 and the CaZrO3 is synthesized by a solid phase method by the prior chemical materials. The medium has high voltage resistance reaching over 10 kilovolt/millimeter, specific inductive capacity of between 2,200 and 3,500 and small variance ratio of capacitance temperature, accords with the requirement on X7R property, Y5T and Y5U property, has excellent stability and high security when used, and does not pollute environment.