The invention relates to a ship shore-based automatic and safe power supply method and device. The method comprises the following steps: 1, output electric energy of a ship shore-based power supply center monitors a power quality parameter through a power monitor unit, and the electric quantity is measured by a power terminal measurement unit and led out to a complete power supply unit through a cable; 2, the water level is detected by adopting a water level monitor transmission unit and uploaded to a power supply control unit, and the power supply control unit controls the cable paying-off height in real time according to the data of the water level, so that the complete power supply unit is controlled to be always positioned on a water surface safety position; and 3, a power supplier and a power user record the current power quantity, a power supply start button is started, and power supply is started. According to the ship shore-based automatic and safe power supply method and device, the heights of an interface and a plug socket can be regulated in real time according to a water surface height signal, the electric connector is always guaranteed to be in a safe range, and the aim of safe power supply is realized.