The invention provides an examination and evaluation system for torsional vibration of a shaft system of a nuclear power steam turbine generator unit. The nuclear power steam turbine generator unit is connected with a boosting transformer, the boosting transformer is connected with one end of a transmission line, and the other end of the transmission line is connected with an infinite bus system. The examination and evaluation system comprises three fault points which include the exit fault point located between the generator unit and the boosting transformer, the near fault point located at the end, close to the boosting transformer, of the transmission line, and the transmission line fault point located on the transmission line. The fatigue life losses of the examination section of the shaft system of the nuclear power steam turbine generator unit are calculated under the electrical disturbance working conditions of the three fault points and phase angle error parallelism, the calculated result is compared with the set standard, and therefore torsional vibration of the shaft system of the nuclear power steam turbine generator unit is evaluated. The invention further provides an examination and evaluation method for torsional vibration of the shaft system of the nuclear power steam turbine generator unit. The system and method have universality and practicality, and can be more comprehensive and closer to the practical situation.