The invention discloses a preparation method of a fermented chrysanthemum cold dressing sauce with alpha-glucosidase inhibitory activity. The preparation method specially comprises the following steps: frying spice with big fire, performing grinding for later use, knotting shallots, performing putting into a pot, adding rapeseed oil, performing frying, adding a sweet chili sauce, chopped garlic, chopped onion and water, performing stir-frying, adding spice and a tomato sauce, performing decocting, performing braising with heat, finally, adding seasonings, performing uniform stir-frying and performing taking out of a pot; and then sequentially mixing chrysanthemums with dogwood and longan aril according to a certain proportion, then adding sugar, bifidobacterium and fruit and vegetable zymophyte, performing shaking table fermentation to obtain fermentation liquor, then adding saccharomycetes and acetic acid bacteria into the fermentation liquor, and performing secondary fermentation toobtain a finished product. The fermented chrysanthemum cold dressing sauce with alpha-glucosidase inhibitory activity, capable of remarkably improving biological accessibility has the functions of stably reducing blood glucose, being high in safety and reducing the occurrence rate of cardiovascular complications.