A voltage regulation device employed in a voltage regulation system is for a motherboard power supply. The voltage regulation device includes a first sampling module, a voltage regulation module, a second sampling module, and a main controller. The first sampling module samples current and voltage signals from a power source through the motherboard power supply. The voltage regulation module outputs adjustable drive voltages for the motherboard power supply controlled by the main controller. The second sampling module samples current and voltage signals of the drive voltages from the motherboard power supply. The main controller receives the current and voltage signals, and converts the current and voltage signals from the first sampling module and the second sampling module to corresponding input power and output power, respectively, and the input power and the output power are calculated to generate conversion efficiencies of each drive voltage.