In order to solve the structural safety design problem of the thermal launch of the marine launch device and to clarify the impact of the jet impact on the marine launch device during the thermal launch process, the characteristics of the plume flow field of the single-nozzle rocket engine is focused on. The computational fluid dynamics method is used based on the k-ω Shear Stress Transfer (SST) model to numerically simulate the plume flow field of the three-dimensional single-nozzle engine, and the variation rules of the temperature, velocity and pressure of the plume flow field with the launch height during the launch process are obtained. The simulation results show that the distance between the nozzle outlet and the deck is of important influence on the shock structure of the flow field, when the distance exceeds 5de (de is the nozzle outlet diameter), the temperature and velocity of the rocket wake drop rapidly, and the deck recovers the environmental pressure when the distance exceeds at 30de. The simulation results can provide experimental reference and theoretical basis for the subsequent safety design of offshore launch platforms and the innovation of diversion devices.