The utility model discloses a device for measuring the vertical span of a power transmission line, comprising a weather detecting function module, a line video monitoring function module, an insulator-string tension detecting function module and an insulator-string angle detecting function module which are respectively and electrically connected with a data processing function module, wherein the data processing function module is electrically connected with a data output function module which realizes the output of results of the data processing function module to an ice real-time monitoring system and is electrically connected with the ice real-time monitoring system. The device disclosed by the utility model has the advantage that the problems that in the process of actual operation of the power transmission line, as the ice real-time monitoring system adopts the theoretical vertical span in the line design as an input value for monitoring, the ice real-time monitoring system of the power transmission line is influenced by environment to cause large error and low accuracy and the like are solved.