The invention relates to a multi-stage pump rotor (10) for a turbo molecular pump. The pump rotor (10) has at least two separate blade disk rings (17), each having a rotor ring (12) and at least one blade disk (14). A cylindrical reinforcement pipe (18), which surrounds the rotor rings (12) of the blade disk rings (17) on the outside without clearance, is provided between the blade disks (14) of adjacent blade disk rings (17). The reinforcement pipe (18) absorbs a large part of the tangential forces occurring during operation such that the pump rotor (10) has improved stability at high rotor speeds.