The present invention relates to a door operator with an abnormal voltage protection function and a method for abnormal voltage protection of a door operator. According to the present invention, before a door operator motor is electrically energized by an external power source, a controller determines whether the external power source meets the rated voltage of the door operator. In the case that the external power source meets the rated voltage, the controller activates the door operator motor; in the case that the external power source does not meet the rated voltage, the door operator motor is deactivated, and the controller issues a warning.