The embodiments of the present invention disclose a single board energy-saving device, which includes: a power calculation module, configured to detect the input current of the single board, and calculate the real-time power of the single board according to the detected input current and a previously measured and obtained input voltage of the single board; a single board energy-saving control module, configured to determine the load condition of the single board according to the real-time power of the single board and send a voltage adjustment command according to the load condition; a power supply adjustment module, configured to receive the voltage adjustment command and adjust the bus voltage of the single board according to the voltage adjustment command. The corresponding embodiments of the present invention also disclose a single board energy-saving method and a single board. Through the foregoing technical solutions, energy-saving is realized for the single board.