A power supply for a redundant power system includes a housing, a first circuit board, a second circuit board and a cooling fan. The first and second circuit boards are sequentially disposed in the housing. The length of the first circuit board is smaller than that of the second circuit board. Between the first and second circuit boards is a gap. The first and second circuit boards are each distributed with multiple electronic elements, and are connected by at least one electrical connecting line. The electronic elements form a power supply circuit, in which a bridge rectification module is disposed on the first circuit board and close to the gap. The cooling fan is at least connected to the first circuit board and a second circuit board to locate in the gap, and directly provides the bridge rectification module with a first cooling air current when activated.