To reduce the static load of the launch rocket systems, dynamic analysis the support of multiple launch rocket systems. According to a canister’s multiply launch rocket system on vehicle platform, using rigid multi-body dynamics and flexible body dynamics theories, establishing the coupled rigid and flexible multi-body system. Using ANSYS and Recurdyn software, flexible carriages are established in ANSYS and imported in the model by the Recurdyn. Launch dynamics simulation and analysis of the model under three conditions where the hydraulic carriages were placed. The result of the simulation indicated: setting the hydraulic carriages in middle was more suitable and, which reflected the real condition.