Improved dual-input power supply

The present invention provides an improved dual-input power supply including a dual-input terminal, an input source selection controller, a load adjustment switch circuit, a power conversion circuit, an automatic switch circuit for power interruption, and an output terminal. The input source selection controller is adapted to select a mode for power inputting comprising AC power source in priority mode, DC power source in priority mode, and dual-power source supply (AC and DC power sources simultaneously supplying) mode. Therefore the present invention allows users to select flexibly power source input mode and maintains uninterruptible power supply by switching automatically the power source input mode upon accident power failure.