The invention provides a chrysanthemum fermentation product and a preparation method thereof. The preparation method of the chrysanthemum fermentation product comprises the following steps of performing rehydration and mashing on chrysanthemums so as to obtain chrysanthemum pulp, inoculating the chrysanthemum pulp with seed liquid, performing fermentation until the content of reducing sugar in obtained fermentation liquid is lower than 1%, and performing homogenizing and sterilizing on the fermentation liquid so as to obtain the chrysanthemum fermentation product, wherein the seed liquid is obtained through the steps of inoculating culture mediums with lactobacillus brevis, leuconostoc mesenteroides, lactobacillus paracasei, lactobacillus casei and lactobacillus plantarum respectively, andperforming extended culture, and the culture mediums comprise the following components of a nitrogen source, a carbon source, inorganic salts, an accelerant, an inhibitor and a chrysanthemum extract.Through the adoption of the preparation method provided by the invention, functional compositions in the chrysanthemums can be sufficiently reserved, so that the chrysanthemum fermentation product has favorable capacity of resisting oxidation, favorable capacity of eliminating .OH free radicals and favorable capacity of eliminating DPPH free radicals.