A power supply apparatus for a power amplifier, comprising a first power circuit, a second power circuit, a gate voltage circuit, an enable circuit, a power-off holding circuit and a detection and control circuit, characterized in that: the power supply apparatus further comprises a redundant circuit connected to the first power circuit, the second power circuit, the power-off holding circuit and the gate voltage circuit, and configured to supply an input voltage to the power-off holding circuit after performing redundancy on an output voltage of the first power circuit and an output voltage of the second power circuit, and to supply an input voltage to the gate voltage circuit after performing redundancy on the output voltage of the first power circuit and an output voltage of the power-off holding circuit, wherein the redundancy refers to the realization of "OR" power supply of a plurality of voltages, that is, selectively supplying power, where the plurality of voltages does not affect each other, and the normal operation of the system can be guaranteed as long as at least one of the voltages is normal; the power-off holding circuit is connected to the gate voltage circuit, and configured to provide power-off energy holding and power-off delay to a gate voltage output by the gate voltage circuit; and the detection and control circuit is connected to the power-off holding circuit, the gate voltage circuit and the enable circuit, and configured to inspect the power-off holding circuit during a power-on process, to detect a voltage of the power-off holding circuit and a voltage of the gate voltage circuit during a normal operation and a power-off process, and to realize, by enable control of the enable circuit, where a detection result satisfies a judgment condition, that power-on of the gate voltage is earlier than power-on of a drain voltage output by the second power circuit and that power-off of the gate voltage is later than power-off of the drain voltage output by the second power circuit. the power supply apparatus further comprises a redundant circuit connected to the first power circuit, the second power circuit, the power-off holding circuit and the gate voltage circuit, and configured to supply an input voltage to the power-off holding circuit after performing redundancy on an output voltage of the first power circuit and an output voltage of the second power circuit, and to supply an input voltage to the gate voltage circuit after performing redundancy on the output voltage of the first power circuit and an output voltage of the power-off holding circuit, wherein the redundancy refers to the realization of "OR" power supply of a plurality of voltages, that is, selectively supplying power, where the plurality of voltages does not affect each other, and the normal operation of the system can be guaranteed as long as at least one of the voltages is normal; the power-off holding circuit is connected to the gate voltage circuit, and configured to provide power-off energy holding and power-off delay to a gate voltage output by the gate voltage circuit; and the detection and control circuit is connected to the power-off holding circuit, the gate voltage circuit and the enable circuit, and configured to inspect the power-off holding circuit during a power-on process, to detect a voltage of the power-off holding circuit and a voltage of the gate voltage circuit during a normal operation and a power-off process, and to realize, by enable control of the enable circuit, where a detection result satisfies a judgment condition, that power-on of the gate voltage is earlier than power-on of a drain voltage output by the second power circuit and that power-off of the gate voltage is later than power-off of the drain voltage output by the second power circuit.