In a volume control method applied to an audio processing system, firstly, a digital audio stream including a plurality of digital audio packets is received from a transmitter. It is determined whether an excitation signal is detected. The digital audio packets are sampled within a predetermined sampled period according to codecing rules, on condition that the excitation signal is detected. Output values corresponding to the digital audio packets are retrieved from the sampled digital audio packets according to the sampling operation. The digital audio packets are analyzed to generate sums of sampled frequency. An averaged volume level is calculated according to the sums of sampled frequency. An audio shift value is generated according to the averaged volume level and a predetermined standard volume level. Volume control is implemented to subsequently received digital audio packets from the digital audio stream according to the audio shift value.