To investigate the superposition effect of the leading edge (LE) film on the downstream film cooling under swirling inflow, numerical simulations with three vane models (vane with films on the leading edge only, vane with films on the pressure side (PS), and suction side (SS) only, full-film cooling vane), two inlet conditions (axial inlet and swirling inlet) are conducted. The results indicate that the leading edge is the area where the film is most affected by the swirling inflow. For full-film cooling vane, the film on the leading edge does not always improve or even reduce the downstream film cooling. Flow mechanism analysis shows that the velocity direction near the downstream wall is governed by the interaction between the direction of swirling inflow and the direction of film hole incidence on the leading edge. A new type of leading-edge film proposed by the author is also investigated, with the dividing line of the counterinclined film-hole row coinciding with the twisted stagnant line to ensure that all films are incident at angles inverse to the direction of the swirling inflow. The new leading-edge film successfully changes the velocity direction near the downstream wall and suppresses the deflecting effect on the downstream film. The new leading-edge film can increase the overall area-averaged cooling effectiveness () of the full-film cooling vane by 10%, 15%, 18% and reduce the inhomogeneity by 13%, 19%, 27% over the traditional design, as the coolant mass flow increases.