The present invention provides a wireless earphone, wherein the wireless earphone includes a first pin, a microprocessor and a power management unit, the first pin is arranged to connect to an external charging device, the microprocessor includes a core circuit and a wakeup circuit coupled to the first pin, and the power management unit includes an uninterruptible power area for providing a power to the wakeup circuit. In the operations of the wireless earphone, when the core circuit is at a sleep mode, if the wakeup circuit detects that a voltage level of the first pin changes, the wakeup circuit generates a wakeup signal to wake up the core circuit.