The utility model discloses a transmission line line is outer broken warning monitoring device of construction down belongs to electric power facility protection technical field, including host system, ranging module, acousto -optic warning module and video surveillance module, host system's input and ranging module are connected, the output is connected with acousto -optic warning module and video surveillance module respectively. Through setting up ranging module, with wire probe distance's detection when the wire protection zone is close to moving object such as ground distance measurementand large construction machinery or vehicles in the monitoring wire way, the host system distance that the measurement obtained to ranging module is judged, at the circuit to ground distance or foreign matter vehicle during to the unsatisfied safe distance of the probe distance of wire, it reports to the police to trigger the sound and light warning module, warning operating personnel dodges the wire, notice maintain the safety distance constantly, accomplish two -way real -time warning, improve reaction rate and the control ability of fortune dimension personnel to the on -the -spot condition.