The invention discloses a wireless earphone and an alarm method thereof. The wireless earphone comprises a left earphone body and a right earphone body, and the left earphone body and the right earphone body are both internally provided with a main control unit, a short-distance wireless communication unit and an alarm unit; the short-distance wireless communication unit in the left earphone bodyand the short-distance wireless communication unit in the right earphone body are in short-distance wireless communication connection. During normal wearing, the distance between the left earphone body and the right earphone body is within a short-distance wireless communication distance, and once the left earphone body or the right earphone body falls off from the ear, communication of the short-distance wireless communication units cannot be achieved. Meanwhile, the main control units judge whether or not the short-distance wireless communication units electrically connected with the main control units achieve short-distance wireless communication, and if not, an alarm signal is generated, the alarm units are controlled to give an alarm according to the alarm signal, and a user is notified that the earphone falls off. Therefore, according to the wireless earphone and the alarm method thereof, the earphone is effectively prevented from being lost.