A traditional Chinese medicine composition for treating diabetes and a preparation method thereof, the composition comprises dried tangerine peels and dark tea. The preparation method utilizes Pu'er tea to shuffle placement with the dried tangerine peels to preserve the dried tangerine peels, mixes different kinds of dried tangerine peels of different aging years, adds the mixed dried tangerine peels with pile-fermented black tea, presses the mixed black tea into tea bricks, and secondarily-ferments the tea bricks, then ages the secondary fermented tea bricks for two years.
