The invention discloses a fermented soybean ointment and a preparation method thereof. The fermented soybean ointment is prepared from the following ingredients in parts by weight: 30-50 parts of fermented soybean powder, 20-35 parts of white spirit, 0.01-5 parts of water-soluble seaweed dietary fiber agar, 1-5 parts of siraitia grosvenorii powder, and 1-5 parts of salt. The product is brownish yellow in color, full-bodied, aromatic, as oily as the fresh ointment after long-term preservation, and free of mildewing, souring, damping and mashing; the used raw materials adopt natural ingredients, and are rich in nutritional ingredients; the fermented soybean ointment is particularly suitable for being used as soy sauce for cooking pork, dog meat, mutton, beef, tofu, steamed fish and pork ribs, and is a good seasoning; the fermented soybean ointment further can be used for treating cold damage febrile disease, chills and fever, headache, dysphoria and choking sensation in chest, has the effects of relieving exterior syndrome, relieving restlessness, removing stasis and removing toxic materials, is free of sugar, low in fat and suitable for patients with hyperlipidemia, high blood pressure and diabetics and weight-losing crowds.