The invention provides a low-clearance single-line tunnel overhead line system suspension structure. A carrier cable suspension device and a contact line locating device of the structure are fixed tothe two side walls of a tunnel, and the carrier cable suspension device is located above the contact line locating device. The carrier cable suspension device comprises a bow-shaped base, a compositeinsulator, a suspension base and a hanging pulley, the front end of the bow-shaped base is cooperatively connected with the rear end of the composite insulator, the front end of the composite insulator is fixedly connected with the suspension base, and the hanging pulley is hinged to the position below the front end of the suspension base. The contact line locating device comprises a bow-shaped base, a connecting double-lug, a rotating double-lug, an elastic insulation limiting locator and a locating cable clamp; and the connecting double-lug is fixed to the front end of the bow-shaped base, the front end of the connecting double-lug is hinged to the rotating double-lug, and the rear end of the elastic insulation limiting locator is hinged to the front end of the rotating double-lug and connected through an elastic pull rod. The suspension reliability, stability and elastic uniformity of an overhead line system are improved, the current collecting quality of a pantograph is improved, and the requirement for continuous increase of the line operation speed is met.