Abstract: The impact and interference effect of the rocket combustion exhaust plume is an important issue related with the launching stability and the ground equipment, including the rocket launcher and the flow channel. Based on the PISO algorithm, numerical simulations of the combustion process and the plume flow field of a hydrogen-oxygen liquid rocket are carried out by solving the Navier-Stokes equation. The impact flow field when the exhaust plume is impacting the ground is obtained. The results show that the physical model, the numerical method and the flow field are reasonable. The pressure and the temperature increase greatly because of the impact and interference effect of the plume. During its impacting ground, in the plume, a high temperature zone appears with a high temperature level near the ground and with low velocities. The most important impact and interference effect shows in the ground area under the exhaust plume, and the main interference zone is in a circular area with a radius of 15 m.