The utility model relates to a portable transmission line sag observation rod belongs to the transmission line construction and overhauls, checks and accepts technical field. Technical scheme is: be equipped with perforating hole (6) on cassette (1), the higher authority of perforating hole (6) is equipped with draw -in groove (4), and the central line of perforating hole (6) is on a parallel with draw -in groove (4), and perforating hole (6) are passed in telescopic link (3), the upper portion of cassette (1) is equipped with screw (5), the central line perpendicular to draw -in groove (4) of screw (5), and fixing bolt (2) set up on cassette (1) perpendicularly through screw (5). The beneficial effect of the utility model: reduced size, convenient to carry, nimble accurate, installation is simultaneously dismantled simply, has avoided traditional observation board to need the fixed mode of rope ligature, and the practicality is strong.