The utility model provides a conjoined fin of a Tuoba boat. A boat fin is arranged at the tail part of a boat body; the boat fin can be hinged on the boat body by a column pin to swing from side to side; the Tuoba boat can very conveniently make use of side-to-side swinging of the boat fin to change the advancing direction of the Tuoba boat during rapidly moving in the water; a pull rope for pulling the boat fin to swing from side to side is arranged on the boat fin; and the pull rope extends to a pedal in a control cabin; and a user can pull the pull rope through stepping on the pedal by left and right feet so as to pull the boat fin to swing from side to side. According to the utility model, the boat fin and the tail part of the boat body are integrally designed, so that convenience in use is achieved; and when the Tuoba boat is idle and stored, large space is not needed by the boat fin, so that great convenience is brought to people.