A method of manufacturing a thin film transistor array substrate to prevent damage to a pad is disclosed. The method includes forming gate lines and data lines that cross each other on a lower substrate, a gate insulating film located between the gate and data lines, a thin film transistor formed at every crossing, a lower gate pad electrode connected to the gate, and a lower data pad electrode; forming a passivation film on the substrate provided with the gate insulating film; forming a photo-resist pattern on the substrate provided with the passivation film; forming a first hole passing through a portion of the passivation film and a portion of the gate insulating film; removing the photo-resist pattern; forming a second hole exposing the lower gate pad electrode; and forming a transparent electrode pattern including an upper gate pad electrode connected to the exposed lower gate pad electrode.