The invention discloses flat-shape black tea and a preparation method thereof. The preparation method comprises the following steps: (1) freezing, namely freezing fresh leaves for 20-28 hours at the temperature ranging from -30 DEG C to -40 DEG C until ice crystals are produced on the outer surface of blades of the fresh leaves, so that frozen leaves are obtained; (2) dehydrating, namely carrying out blast dehydration on the frozen leaves for 1-2 hours at the temperature of 35-40 DEG C, so that dehydrated leaves are obtained; (3) fermenting, namely fermenting the dehydrated leaves for 6-10 hours at the fermentation temperature of 35-40 DEG C, so that fermented leaves are obtained; (4) pressing and forming the fermented leaves; and (5) drying. The obtained flat-shape black tea is uniformly fermented, no mixed part is formed, the shape is flat, and a golden tip is obvious; meanwhile, liquor colour and phyllotaxes are red brilliant, fragrance is strong, taste is mellow, and dust ratio of the product is low.