The preparation method comprises the following steps: adding a catalyst into heated long-chain
alkyl benzoic acid under a stirring condition, adding 3-dimethylamino-1-
propylamine in a
nitrogen atmosphere, carrying out a heating reaction, and carrying out suction
filtration, washing and
drying to obtain the long-chain
alkyl phenyl hydroxy sulfobetaine surfactant for
oil displacement. Carrying out reduced pressure
distillation on the product, and carrying out suction
filtration to obtain brown yellow liquid which is
tertiary amine; then uniformly mixing a
solvent and
tertiary amine, adding 3-chloro-2-hydroxy propyl
sodium sulfonate, adjusting the pH value, carrying out
reflux reaction, and carrying out reduced pressure
distillation on the product to obtain a crude product; and adding
ethanol into the crude product, filtering, and carrying out rotary
evaporation to remove
ethanol, thereby finally preparing the long-chain
alkyl phenyl hydroxyl sulphobetaine surfactant. The preparation method is lower in
reaction temperature and shorter in reaction time; in the step S2, an
ethanol water solution is used as a reaction medium and is more environment-friendly; the crude product produced in the step S2 is subjected to
impurity removal by using an ethanol
aqueous solution, so that the method is more environment-friendly.