The invention discloses a turbomachinery single supporting shafting geometric centering installation method, which comprises the following steps: (1) constructing a single supporting shafting dynamic finite element model which is in accord with an actual structure and operating parameters; (2) determining impeller and disc places as residual unbalance applying position points for each rotor in a shafting; (3) simulating residual unbalance phase combination conditions among shafting rotors; (4) analyzing shafting steady-state responses under different residual unbalance applied combinations, and finding out a residual unbalance phase optimal combination for each rotor under minimum shafting vibration; and (5) on the basis of traditional shafting centering, according to residual unbalance information recorded in a high speed dynamic balancing report before each single rotor leaves a factory, and according to the phase optimal combination, carrying out shafting geometric centering installation. According to the method disclosed by the invention, the problem of over-standard vibration due to a fact that a turbine unit has a qualified single rotor dynamic balance but has an unbalanced shafting after installation and test run is solved, the installation time is reduced, and the installation efficiency is improved; and the method has relatively good operability and practicability.