The invention discloses a preparation method of a silica gel sealing medium partition plate, relating to a preparation method of a heat-resistant sealing gasket. The silica gel sealing medium partition plate comprises the following raw material components in parts by weight: 100 parts of dimethyl siloxane and vinyl siloxane polymers, 50 parts of special white carbon black for silicon rubber, 2 parts of zinc oxide, 6 parts of silane, 10 parts of silicon hydride oil, 1 part of DBPMH (2,5-dimethyl-2,5-di (tert-butylperoxy) hexane) and 1.5 parts of boric acid ester and is prepared by copolymerizing, forming and vulcanizing the raw materials in parts by weight per se. The silica gel sealing medium partition plate is formed by copolymerizing dimethyl siloxane and a small amount of vinyl siloxane, wherein the content of vinyl is 0.1%-0.3%, the tensile strength of a finished product reaches 7.2 MPa, the elongation at break reaches 600%, the hardness reaches 61 (A), the breakdown voltage reaches 19 Mv/m, the volume resistance reaches 9.2*1014 omega.cm, the brittleness temperature reaches -65 DEG C, and the using temperature range is -50 DEG C-+250 DEG C.