A power redundant system includes a switch module, a power-supplying module and a control unit. The switch module includes switch units. Each switch unit switches a power as an input power. The power-supplying module includes power-supplying units. Each power-supplying unit is connected to a switch unit correspondingly and converts the input power into an output power and supplies the output power to a load. The control unit controls the switch units to switch one of input sources of the power as the input power. If one of the switch units or power-supplying units is not operational, an electric power supplied by the power-supplying units connected to the remaining switch units correspondingly is greater than or equal to an electric power required by the load. When one of the input sources is abnormal, the control unit controls the switch units to switch to another input source.