To study the adaptability of the modularized Marx generator in mechanical environment, simulation and vibration experiment of the generator are conducted based on the random vibration theory and finite element analysis method. Firstly, the finite element simulation model of an 8-stage Marx generator is established, and the stress concentration positions are identified. Secondly, the finite element model is corrected according to the initial results of shaking table test. Then an optimization scheme is proposed to modify the Marx generator. As a result, the first-order frequency of the Marx generator is increased from 15.4 Hz to 19.7 Hz. It is helpful to reduce the dynamic response in vertical direction and enhance the mechanical environment adaptability. Results show that more attention should be paid to the reliability in vertical direction when a Marx generator is being designed. The connection of the generator is stable in the vibration experiment, and the stresses mainly concentrate on the corner pieces between the generator and the U-shape support plates, the connections between U-shape support plates and side support plates, and the switch junctions, which are the weak points in design.