The invention discloses a flat plate unit of a bicolor aluminum product. The flat plate unit of the bicolor aluminum product comprises a left flat plate unit body and a right flat plate unit body. An upper caulking groove is formed in the right edge of the left flat plate unit. An upper hook piece is arranged on the left edge of the right flat plate unit. The upper caulking groove comprises an upper caulking groove wall, the upper surface of the upper caulking groove wall is flush with the upper surface of the left flat plate unit body, a lower caulking groove wall is located below the upper caulking groove wall, and a first barb is arranged at the right end of the lower caulking groove wall. The left section of the upper hook piece is embedded into the upper caulking groove and abuts against the upper caulking groove wall, and a second barb stretches out of the right end of the upper hook piece and is connected with the first barb in a hooked mode. A left torsion-preventing plate and a right torsion-preventing plate are arranged in the space below the lower caulking groove wall and abut against each other and/or are connected with each other in a hooked mode after stretching towards each other in the left-right direction. Through the embedding and hook-connecting structure of the upper caulking groove and the upper hook piece, the left unit body and the right unit body can be prevented from being separated from each other, the two torsion-preventing plates prevent components from rotating around the right end of the upper caulking groove, the torsional force application range of a joint is dispersed, and the components are more difficult to separate. The flat plate unit of the bicolor aluminum product is reliable and firm in structure, the torsion resistance is high, and the flat plate unit can serve as an aluminum profile.