A dynamic pulse width modulation (PWM) amplifier comprising an input terminal, a dynamic PWM controller, a power stage, a low pass filter, and an output terminal. The input terminal receives an input signal. The dynamic PWM controller transforms the N-bit input signal sampled by a sampling frequency to a 1-bit PWM signal. The power stage receives and outputs the 1-bit PWM signal. The low pass filter receives and outputs the 1-bit PWM signal. The 1-bit PWM signal is used to drive the power stage and the low pass filter. The output terminal outputs the 1-bit PWM signal. The dynamic PWM amplifier is characterized in the dynamic PWM amplifier uses a register array to store the input signal processed immediately in each frame, regroups the input signal, and outputs the regroup signal, so that the 1-bit PWM signal is changed according to the input signal.