For the vibration of the flexible modular crane in a workshop tending to have large amplitudes and slow degradation during lifting of the workpiece, field vibration tests were carried out on the whole lifting system. Via the tests, the reinforcement schemes were proposed to reduce the vibration amplitude of the system by improving the dynamic stiffness. Finite element models were developed to simulate the whole lifting system and to investigate the dynamic response of the system under an inertial impact load caused by a sudden pause happening during the lifting of a workpiece, The effect on vibration reduction of the system was verified through simulation analysis, which can provide references for installation and solving vibration problems of such cranes.