A high-precision tensioning device is provided. The high-precision tensioning device is composed of a stepping motor, an encoder, a harmonic reducer, a rotary table, connecting rods, contacts, force sensors, a rotary table connecting piece, a gasket, a nut, bolts, a set screw, a shell and an end cover. The tensioning device provided by the disclosure can achieve closed-loop control on a tensioning force in order to improve the tensioning precision of the tensioning device; and as long as machining and assembling errors meet design requirements, stable synchronous tensioning of three contacts can be ensured, and the location precision of a hub is improved.