The invention discloses a preparation method capable of improving yield of an alpha-isomer in an ionone product. The method comprises the following steps of: 1, preparing a spurious ionone product and an ionone after-cut product with beta-isomer content of 35% or more; 2, adding acid solution and an organic solvent, of which a quantity occupies for half of a total quantity of catalyst acid solution, into a container, then adding the ionone after-cut product, uniformly stirring, heating to a temperature of 35 to 80 DEG C, dropwise adding the spurious ionone product, completing replenishment of the residual acid solution after finishing dropwise adding, and continuously keeping the temperature to stir for 1 to 4 hours; 3, after completing the reaction and standing, separating out viscous acid solution on the bottom layer, washing an organic phase on the upper layer to a neutral state, and after recovering the solvent, carrying out vacuum rectification to obtain a high-content alpha-ionone product with alpha-isomer content of 86% or more. According to the preparation method disclosed by the invention, yield of the alpha-isomer in the ionone product is effectively improved, and the preparation method is simple, economic, practical and suitable for industrial continuous production of high-content alpha-ionone.