The invention relates to a preparation method of an edible oil leaching agent, in particular to a preparation method of the leaching agent used in edible oil industries; and the preparation method comprises the following steps of: taking aromatic raffinate oil refined by petroleum as a raw material, and by using a fibrous membrane contactor, carrying out washing and desulfuration, dehydration, hydrogenation deolefination, hydrogenation dearomatization, distillation and the like so as to obtain the leaching agent with high quality. The preparation method has the advantages of increasing the product quality and recovery rate of a solvent, decreasing residual oil in oil residuals, reducing the solvent loss and energy consumption, being beneficial to increasing the quality of oil and oil residuals, having no influence on environments and being safe to human bodies.