The invention discloses a seaweed mung bean cake and a preparation method thereof. According to the seaweed mung bean cake and the preparation method thereof, laminarin, mung beans and agar are takenas main raw materials, and the method comprises the following three production steps: extraction of the laminarin, forming of seaweed mung bean cake blanks and preparation of seaweed mung bean cake finished product. According to the seaweed mung bean cake of the invention, the block shape is neat, the pattern is clear, and the edge is not rough; the color is yellowish, the surface is fine and glossy, and the color is uniform and matches with the rose red transparent agar layer so as to complement each other; the tissue is soft and delicate, non-sticky and free from impurities; the flavor is fragrant and delicious, and oily and sweet; in function, the cake is capable of regulating immunity, expelling toxins, beautifying skins, lowering blood pressure, lowering blood sugar and preventing cancer, and is suitable for people of all ages.