The invention discloses a marine tangential pump, which comprises a motor, a bracket, a pump body, a pump shaft, a sealing expansion part, a mechanical seal, a gland, an impeller, a pump cover and a nut. The bracket is directly connected to the motor and the pump body. The mechanical seal and seal expansion parts are installed on the pump shaft. The gland and the pump body cooperate to not only axially position the mechanical seal but also form a sealing cavity for storing lubricating oil. The impeller is installed at the end of the pump shaft and locked by a nut to rotate with the motor. The pump cover cooperates with the pump body to form the pump chamber where the impeller is placed. In the present invention, the impeller is an open structure, which is in the shape of a gear in the axial direction, and 8 to 16 radial blades of alternate lengths are exposed and evenly distributed on the side plate surface, and axial balance holes are arranged between the long and short blades. The radial blades are wide inside and narrow outside. In the invention, the friction loss of the impeller disk is small, the axial force is small, the structure strength is high, and the impact resistance is strong. In addition, the cooling condition of the mechanical seal is good, and there will be no excessive temperature difference with the medium, so it is not easy to be damaged.