The shift lever of dispensing device in charge feeding mechanism should contact with the locker device of the cartridge case in a very short period of time and let modular charge get out from the cartridge case. In order to study the impact of high-speed movement on moving parts, the shift lever was created as flexible body by Ansys software and was established rigid-flex coupling dynamics models with ADAMS software. Compared with the original multi-rigid-body dynamics model, the following conclusions can be obtained: velocity-response curve of the shift lever with flexible body will fluctuate under the action of external force and the shift lever with rigid body will not; the contact force calculated by the simulation of the flexible body collision is smaller than it calculated by the simulation of the rigid body collision. The reason for the above result is that the flexible body part is elastically deformed during the movement. The study of the modular charge feeding mechanism in the modular supply device has a reference role.