Abstract: A display device includes a display module, a control module, a power supply module, and a power monitoring module. The control module is signally connected to the display module. The power supply module is electrically connected to the control module. The power supply module includes an input terminal and an output terminal. The input terminal receives input electricity. The output terminal outputs output electricity to the control module. The power monitoring module is electrically connected to the power supply module and the control module. The power monitoring module monitors an output power of the output electricity and an input power of the input electricity and calculates a power loss ratio according to the output power and the input power. When the power loss ratio is less than a loss threshold, the power monitoring module generates a first notifying data according to the power loss ratio.