The invention provides a burdock fermented product and a preparation method thereof. The method comprises the steps of 1) cleaning and crushing burdock, adding water to obtain burdock liquid, and adding pectinase and cellulase for enzymolysis to obtain enzymolysis liquid; 2) adding a carbon source, a nitrogen source and an inorganic salt into the enzymolysis liquid, inoculating leuconostoc mesenteroides for primary fermentation, thus obtaining primary fermentation liquid when the pH value of the fermentation liquid is reduced by more than 0.5; 3) adding a carbon source and a nitrogen source into the primary fermentation liquid, inoculating compound lactobacilli for second fermentation, thus obtaining second fermentation liquid when the total sugar content of the fermentation liquid is less than 3wt%, wherein the compound lactobacilli comprise streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus and lactobacillus plantarum; and 4) blending the second fermentation liquid uniformly, centrifuging, and homogenizing and sterilizing the centrifugal supernatant to obtain the burdock fermented product. By adopting the scheme, the burdock fermented product with low sugar content, good mouthfeel and unique flavor can be obtained within a short fermentation time.