Disclosed is a circuit structure for implementing an adaptive function in a class-D audio power amplifier circuit, comprising an operation amplifier, a pulse width modulator and a driver stage that are sequentially and serially connected, an input terminal of the operation amplifier being connected to an external audio signal output terminal, and an output terminal of the driver stage being connected to a loudspeaker and connected to the input terminal of the operation amplifier via a feedback loop. The circuit structure further comprises: one or a plurality of a carrier adaptive circuit, a frequency adaptive circuit, a driver adaptive circuit, a temperature adaptive circuit.