Disc-rotor is composed of certain number of discs which are fastened as a single-shaft rotor by tie-rods. The rods must be very carefully tensioned in the course of rotor assembly to ensure a circumferentially uniform prestress, thus acceptable run-out value, as otherwise the rotor will be susceptible to vibrations particularly during start-up. Uniform prestress is also beneficial to improve the fatigue life of the rods. Initial preload for one rod is calculated and the appropriate tightening scheme is determined by finite element analysis, considering relaxation and elastic interaction. A kind of hydraulic tensioner is designed to assemble the disc-rotor. The experiment to fasten the disc-rotor by the tightening scheme above mentioned is presented.