The invention relates to a power line wire tightening balance measuring device, which consists of a wire clamp, a sag measuring instrument and a wire tightening device, wherein the wire clamp is connected with a movable rod of the sag measuring instrument; a wire pulling hook of the wire tightening device is connected with a fixing buckle of the sag measuring instrument; the wire clamp is a wire clamping device with a wedge-shaped structure; and the sag measuring instrument is a sag measuring instrument capable of automatically converting the distance between the towers, the wire diameter, theenvironment temperature value and the wire tension measured in the wire tightening process into sag values and displaying the sag values through a display device. The wire clamp is of a wedge-shapedstructure, so that the wire clamp is convenient to mount and dismount, the wire clamp is pulled tighter and tighter, and the wire is effectively prevented from moving in the wire tightening process; as the sag measuring instrument is arranged, the sag of each wire is ensured to be consistent, the design requirement of the sag of the line can be met, and the measurement is convenient; and the device is simple, safe, reliable and convenient to use, so that the device has great practical and promotional values.