The present invention provides a PAM (Pulse Amplitude Modulation) method and circuit for improving the performance of a D-class audio amplifier. The D-class audio amplifier is inputted with a PWM signal and designed to have a dead time function for time delay. In order to decrease the distortion of the output signal caused by the dead time design, the present invention comprises the following steps:detecting the polarity of the current of an output terminal of the D-class audio amplifier; adding a voltage adjustment circuit to a power source of the D-class audio amplifier to lower the voltage of the power source of the D-class audio amplifier from high voltage to low voltage during dead time when the polarity of the current is negative; adding a voltage compensation circuit to a low voltage point of the D-class audio amplifier to compensate the voltage of the low voltage point of the D-class audio amplifier for ascending the voltage of the low voltage point from low voltage to high voltage during the dead time when the polarity of the current is positive.