The invention provides an automatic switching device and system of power amplifiers. The device comprises a control bus, an input signal switching channel and an output signal switching channel; the input signal switching channel comprises a test signal input port, a first changeover switch and power-amplification signal input ports; the first changeover switch comprises a first control end and multiple first switching ends; the first control end is connected to a signal generator via the test signal input port; each first switching end is connected to one power amplifier via one power-amplification signal input port; the output signal switching channel comprises a signal output port, a second changeover switch and power-amplification signal output ports; the second changeover switch comprises a second control end and second switching ends; each second switching end is connected to one power amplifier via one power-amplification signal output port; the second control end is connected to an emission antenna via the signal output port; and the control bus is connected with both the first and second changeover switches.