Abstract: The Realizable k-ε turbulence model，the mixture multiphase model and the dynamic layering mesh update method are used to investigate the interior ballistics of a new independent water-surface launching canister，and analyze its influencing factors by modeling the relative motion between the missile and the canister. The interior ballistics and the internal flow characteristics of canister launcher on water-surface and ground are analyzed and compared numerically，and the influence of the canister emerging velocity on the interior ballistics is investigated. Results show that the launchers on water-surface and ground have the similar flow characteristics in the gaps and in the pressures in the low pressure chambers. The exit velocity of the missile on water-surface is faster than that on ground，the maximum missile load on water-surface is 20% less than that on ground，and the launch time for the water-surface launching is 14% less than that on ground.The flow results show that the gas does not directly interact with the water surface，therefore the phase change energy dissipation does not happen.The emerging velocity changes the ejection velocity increment by affecting the force of water on the canister.The nonlinear effect of the emerging velocity on the increment of ejection velocity can be ignored because the buoyancy variation is far less than the gas force，so the exit velocity of missile is a linear superposition of the emerging velocity and the increment of ejection velocity.

Key words: ater-surfacelaunch, independentcanister, layeringmesh, gas-ejection, interiorballistics