Abstract: The near-electricity warning device is an important equipment to ensure safe construction in electric power environments. The mistouch of voltage level selection switches and unstable warning signals across zone boundary in traditional devices was analyzed, and a dynamic zone division method and warning device was proposed. By combining the internal latching of the voltage level selection with electronic analog switching, the mistouch of voltage level switches is prevented during operation. By integrating near-electricity control circuit with ultrasonic ranging, the ultrasonic ranging is initiated to determine whether operator have entered the dangerous alarm zone based on the early warning from the near-electricity control circuit. The boundary between the alarm zone and the warning zone is dynamically adjusted according to the movement of the operator, and then stable output of warning signals was achieved.