The invention belongs to the technical field of fuel cell catalysts, and relates to a preparation method of a binary metal platinum-palladium prismatic catalyst, which comprises the following steps: dissolving a platinum precursor and a palladium precursor in a solvent containing a reducing agent, uniformly stirring, adding a surfactant for dispersion, then adding a carbon carrier, and ultrasonically and uniformly mixing to obtain a precursor solution; and then transferring the precursor solution to a reaction kettle, carrying out hydrothermal reaction at 120-200 DEG C for 16-28 hours, cooling to room temperature, centrifuging, washing with deionized water and absolute ethyl alcohol until no impurity exists, and drying to obtain the product. The method is simple in synthesis process, easy to operate, good in repeatability, capable of being produced on a large scale, high in yield, excellent in product performance and beneficial to commercialized popularization. The synthesized platinum-palladium direct methanol fuel cell alloy catalyst has prismoid morphology, has higher activity and durability compared with commercial platinum-carbon and platinum-ruthenium-carbon, has catalytic performance obviously superior to that of a commercial Pt/C catalyst, and has good application prospect and economic value.