The invention discloses a preparation method of a polyether ketone/sulfone high-temperature resistant material, which comprises the following steps that: firstly, a reactive monomer, a solvent and an inorganic alkali are put into a first reactor, are mixed at a temperature of 40 to 90 DEG C by stirring, and are dissolved; secondly, the mixture is transferred to a second reactor, is added with a water-carrying agent, and is stirred at a temperature of 150 to 280 DEG C to be subjected to salt formation dehydration; and a material after being subjected to salt formation dehydration is introducedinto a third reactor, and is stirred at a temperature of 230 to 330 DEG C to be subjected to polymerization to obtain a product. The synthesis process of the polyether ketone/sulfone material is reacted in three reactors with different temperatures, so that an intermediate product prepared in each step is more sufficient and uniform, the obtained product has a gel content reduced to less than 3% and molecular weight distribution which is more reasonable and reaches the range of 2.42 to 2.45 without changing the comprehensive performance of the product, and thereby the quality of the resin product is improved; and the preparation method is suitable for continuous production, and production cost reduction, energy consumption reduction in a production process and stable quality of the obtained product are achieved.