Abstract: Overhead line system is the high voltage transmission line for pantograph obtaining electric current which is built above the rails in electrified railways. Its key task is to transport the electric energy from traction substation to electric locomotive. Aiming at the problem of low precision and low efficiency in traditional measuring method of geometric parameters, a measuring system is designed which is fast and of high precision. The system is based on principle of binocular vision. It produces the feature using a laser, acquires images using two high-resolution cameras and makes three-dimensional calculation, which makes it possible to measure the geometric parameters of the overhead line system in real time. Experimental result indicates that the repeatability precision of the system can reach up to 1 mm, and that the reliable real-time measurement of geometric parameters of the overhead line system has been accomplished, which provides useful theoretical basis for operating repairs.