An etching process of a metal layer of a display panel is provided. First, a substrate with at least one display panel region, a testing device region, and a non-device region is provided. Then, a metal layer is formed over the substrate to cover the display panel region, the testing device region, and the non-device region. Next, a mask is formed on the metal layer to expose a portion of the metal layer. The area of the metal layer exposed by the mask substantially occupies 70%˜88% of the total area of the metal layer. Thereafter, a wet etching process is performed to remove the metal layer exposed by the mask.