The invention relates to the technical field of organic synthesis, in particular to a preparation method of 3-thiophenecarboxaldehyde. The preparation method of 3-thiophenecarboxaldehyde comprises thefollowing steps: performing reaction on 1,1,3,3-tetramethoxypropane under the acidic condition, performing mixed reaction on the reaction product and 1,4-dithio-2,5-diol under the alkaline conditionand performing aftertreatment to obtain the 3-thiophenecarboxaldehyde. By the preparation method of 3-thiophenecarboxaldehyde, the 3-thiophenecarboxaldehyde product with the purity exceeding 98 percent can be prepared only through simple mixing and stirring reaction, reaction does not need ultralow temperature and dangerous reagents in the preparation process, and the production safety coefficientis increased. Furthermore, the preparation method provided by the invention is simple in operation, the raw materials are easily available, operation cost and raw material cost are reduced, and the preparation method is suitable for industrialized production of 3-thiophenecarboxaldehyde.