The invention relates to a black soybean food which uses black soybean as a main 
raw material and traditional Chinese medicines as auxiliary materials, and a preparation method thereof. The preparation method is characterized by comprising the following steps of: respectively taking prepared Radix Polygoni Multiflori, lucid 
ganoderma, mulberry, 
ligustrum lucidum, black sesame and prepared 
rehmannia root according to a weight ratio of 5 / 12-7 / 12 accounting in the black soybean, adding water, boiling and decocting and then filtering to obtain a liquid 
medicine; then taking pepper, fructus anisi stellati, fennel, cinnamon, 
pericarpium citri reticulatae, angelica, galangal, fructus piperis longi, rhizoma zingiberis, galangal fruit, 
Kaempferia galangal and the like according to the right amount for being mixed and smashed via mesh screen to obtain a 
fine powder seasoning; taking 
halite according to a weight ratio of 1 / 25-1 / 30 accounting in the black soybean, putting the black soybean into the liquid 
medicine for boiling and decocting, adding the 
halite and the fined 
seasoning for adjusting the taste, baking in a heated air circulation oven, and taking out for eating. The black soybean food provided by the invention is rich in 
protein, 
lecithin, fat and 
vitamin, has the functions of activating blood, 
diuresis, dispelling wind, 
detoxication and 
softening the blood vessels and has good 
efficacy for patients suffering from hypertension, 
heart disease and the like.