An audio playback system includes an earphone and an audio device. The earphone includes a first earphone body, a second earphone body, a first sensing unit mounted in the first earphone body, a second sensing unit mounted in the second earphone body, a first plug, and a second plug electronically connected to the first sensing unit and the second sensing unit. The audio device includes a first jack, a second jack configured to receive the second plug, and a control unit. The first sensing unit and the second sensing unit output sensing signals which indicate whether the earphone is used. The control unit receives the sensing signals from the second jack and controls a working state of the audio device.