The invention discloses a high-strength tear-resistant rubber sealing gasket and a preparation method thereof. The high-strength tear-resistant rubber sealing gasket is prepared from raw materials, namely chlorosulfonated polyethylene rubber, silicon rubber, bisphenol A type polycarbonate, cashew nut shell oil modified phenolic resin, hexamethylenetetramine, dicumyl peroxide, spray carbon black, modified nano ceramics, silicon-magnesium-calcium crystal whiskers, nanometer wollastonite, zinc methacrylate, magnesium oxide, stearic acid, vinyl silicone oil, chlorinated paraffin 4-7, triethyl citrate and the like. According to the high-strength tear-resistant rubber sealing gasket and the preparation method thereof disclosed by the invention, the organic composite modification is carried out by adopting multiple nano ceramic powder, namely nanometer aluminum nitride, nanometer titanium carbide and nanometer zirconium boride, so that the compatibility of the nano ceramic powder and rubber can be enhanced; the modified nano ceramic powder, the silicon-magnesium-calcium crystal whiskers, the nanometer wollastonite and the like are filled in a modified rubber material together to prepare the sealing gasket, so that the mechanical strength, impact resistance and especially tear resistance of the sealing gasket can be remarkably improved; the heat resistance, abrasion resistance and the like of the rubber can also be improved.