A method of manufacturing a thin film array panel is provided, which includes: forming a gate line formed on a substrate; forming a gate insulating layer on the gate line; forming a semiconductor layer on the gate insulating layer; forming an ohmic contact layer on the semiconductor layer; forming a data line and a drain electrode disposed at least on the ohmic contact layer, forming an oxide on the data line; etching the ohmic contact layer using the data line and the drain electrode as an etch mask; and forming a pixel electrode connected to the drain electrode.