The invention discloses unique-flavor mushroom beef paste and a preparation method thereof. The mushroom beef paste is prepared from main raw materials of edible fungus mushroom, soybean paste, vegetable oil and lean beef through a special process. The mushroom beef paste is prepared from the following raw materials: 40 to 50 percent of fresh mushroom, 10 to 30 percent of soybean paste, 15 to 35 percent of vegetable oil, 3 to 8 percent of lean beef, 1 to 2 percent of fresh onion, 1 to 2 percent of fresh ginger, 1 to 2 percent of fresh garlic, 1.7 to 3.4 percent of dried red chilli, 1 to 3 percent of edible salt, 1 to 3 percent of white sugar, 0.5 to 1 percent of gourmet powder, 1 to 2 percent of spice (anise, pepper, cinnamon and fennel in a weight ratio of 3:4:2:1), and 0.06 to 0.16 percent of dry onion, ginger and garlic powder (in a weight ratio of 1:1:1). The preparation method comprises the following steps of: cleaning and preprocessing the raw materials, preparing spicy oil, preparing minced lean beef, frying, filling, exhausting and sterilizing. The product ensures the unique flavor of the mushroom, has thick sauce aroma and slightly spicy mouthfeel, can promote appetite, integrates multiple nutrients of the mushroom, the soybean paste and the beef, has good color, aroma and taste, and is a green instant food which is rich in nutrients, delicious in taste, rich in mouthfeel and convenient to eat.