The invention provides a preparation method of high-speed engine base oil, which is prepared by preheating, hydroisomerization, hydrofining, high and low pressure separation, atmospheric distillation, vacuum fractionation, and finally using a composite adsorbent for secondary adsorption refining. Get the target base oil. The invention changes the molecular size, structure and arrangement of oil products, increases ideal components, inhibits coking and carbon deposition of catalysts, reduces the generation of non-ideal components such as polycyclic aromatic hydrocarbons and asphaltenes, improves the quality of oil products, and removes impurities, so that The chromaticity, flash point, and oxidation resistance of the oil have been significantly improved, and the application range and stability of the oil have been significantly improved. The base oil prepared by the invention has the characteristics of high flash point, high viscosity index, low pour point, strong oxidation resistance and high transmission efficiency, and can be better applied to high-speed engines.