An active device array substrate, having a display region and a peripheral circuit region outside of the display region, is provided. The peripheral circuit region has a terminal region and a narrow-edge region between the terminal region and the display region. The active device array substrate includes a pixel array, multiple electrode lines and a testing device. The pixel array is disposed in the display region. The electrode lines are disposed in the peripheral circuit region and electrically connected with the pixel array. The testing device is disposed in the narrow-edge region for inspecting the active device array substrate. After the inspection, an additional cutting process is needless for removing the testing device, so that the process cost is reduced. A liquid crystal display panel with the above active device array substrate is also provided.