According to the problem that the ship-brone MLRS which takes up large deck space and existences blind angle on the direction and height, design a new type of rocket vertical launching system. To verify feasibility of the launch system, used the FLUENT to simulate the launching process of the rocket, and got the jet flow field characteristics and change rules of the bottom of the device. The results show that the pressure of the bottom of the device is small in the process of launching, which doesn't threaten the safe operation of the engine, and the increasing force is inconspicuous. Comparing the simulation results and the experiment data in the end, which provides test and theoretical basis for the optimization of the launcher.