A power management system coupled to a speaker module includes a monitor module for measuring a current signal and a voltage signal of the speaker module to obtain a real-time impedance information of the speaker module; a reception module for receiving a time-domain audio analogy signal to be transformed into a frequency-domain audio digital signal; a prediction module for generating a power prediction information according to an initial audio information, the real-time impedance information and the audio digital signal; a control module for generating a control signal according to the audio digital signal and a human hearing model information; and a power adjustment module for outputting an adjustment audio signal to the speaker module according to the power prediction information, the audio digital signal and the control signal, so as to perform a broadcast operation of the speaker module.