The invention belongs to the field of electrocatalytic materials, and discloses a PtAuPd@Ag core-shell nanocrystal electrocatalyst and a preparation method thereof. The preparation method comprises the steps: dissolving CTAB and glucose in a silver-ammonia solution to obtain a precursor solution; carrying out a reaction at the temperature of 80-180 DEG C, cooling to room temperature, centrifugingthe obtained reaction solution, and then taking the supernatant, to obtain a Ag seed solution; dissolving PVP and citric acid in water, then adding the Ag seed solution, stirring and mixing evenly, heating up to 60-120 DEG C, adding chloroplatinic acid, chloroauric acid and chloropalladium acid, and carrying out heat preservation reaction for 2-8 h; and washing and centrifuging the obtained reaction solution, to obtain the PtAuPd@Ag core-shell nanocrystal electrocatalyst. The preparation method is simple in process, the raw materials are easy to obtain, and the obtained PtAuPd@Ag core-shell nanocrystals have uniform size and morphology, and can be used for preparing high value-added products by catalytic electrooxidation of glycerol.