The utility model relates to a method for preparing high-temperature resistant insulating resin and application thereof. The high-temperature resistant insulating resin resists a temperature of 350 to 450 DEG C and has heat insulation properties. The preparation method comprises the following steps of: 1). mixing molybdenum naphthenate and phenolic resin according to a molar ratio of 1:3 at a temperature of 20-30 DEG C, and in a protective gas environment, gradually heating to 78-89 DEG C and then starting to stir; continuing to heating to 85-115 DEG C, and under the catalytic condition of a soluble magnesium complex, reacting for 40-50 minutes and polymerizing to obtain molybdenu-modified phenolic resin; 2). adding 3-5% by ratio of low melting-point glass powder and 2-3% by ratio of high-temperature stabilizer to the molybdenu-modified phenolic resin, continuously and uniformly stirring to obtain high-adhesion molybdenum-modified phenolic resin material; and 3). adding 20-25% by ratio of long glass fiber or glass fiber fabric and 1-2% by ratio of ceramic fiber to the high-adhesion molybdenum-modified phenolic resin material, kneading and molding into sheet to obtain the high-temperature resistant insulating resin.