Abstract: High-speed-train wing (HSTW) is a new concept for increasing the aerodynamic lift force via installing tandem airfoils on high-speed trains, which has the potential of reducing the total energy consumption and cost during the life cycle of the train. As the wing adds extra lift to the train, the net weight of the train is reduced, subsequenly the friction drag and the wear of the wheel induced by the wheel-rail interaction are also reduced. In order to reduce the aerodynamic interaction between tandem wings, the aerodynamic characteristics of airfoils with different roof-to-wing distances and angles of attack are studied numerically under the constraint of the railway gauge. A prototype of the aerodynamic configuration is proposed, based on which an optimization design of the airfoil is carried out. The results show that there is a significant lift loss when the back wing is located in the wake region of the front wing, and such an aerodynamic loss increases with the increase of the angle of attack. With the optimization of the airfoil, the lift coeficient and the lift-to-drag ratio of the new airfoil are increased by 14.06% and 10.71%, respectively.