A power management method a display device utilizes the same are disclosed. The power management method, adopted by the display device, includes: increasing, by a control circuit, brightness of a lighting device, wherein the lighting device is configured to illuminate a display panel device; detecting, by an overload detection circuit, whether an overload has been triggered by the increased brightness; and when the overload has been triggered by the increased brightness, recording, by a power capacity determination circuit, a maximal predetermined brightness that is used prior to the overload is triggered, while showing an on-screen-display (OSD) warning message on a display of the display device for reminding the user. When the brightness of the lighting device reaches the maximal predetermined brightness and the power capacity determination circuit detects no overload, this indicates the power capacity is sufficient for supplying power to the display device.