A power backplane assembly is adapted to be connected to a power supply. The power supply outputs a first voltage. The power backplane assembly includes a backplane body, a conversion circuit board, and an output circuit board. The backplane body is for plugging in the power supply. The conversion circuit board is electrically connected to the backplane body. The backplane body is adapted to deliver the first voltage to the conversion circuit board. The conversion circuit board converts the first voltage into a second voltage. The output circuit board is electrically connected to the conversion circuit board and includes a first output connector and a second output connector. The first output connector is configured to output the first voltage, and the second output connector is at least configured to output the second voltage. A power supply module which has the power backplane assembly is also provided.