In order to study the effect of the blast deflector’s movement in sea launch on the rocket wake flow field, a combination model of the tail nozzle and blast deflector for certain type of carrier rocket is established. The Computational Fluid Dynamics (CFD) software Fluent is used, and based on the Realizable k-ω turbulence model and the second-order windward format, a transient numerical simulation model of the wake flow field is established. The velocity, pressure and temperature in the rocket wake flow field are studied under the translational and rotational movement of the blast deflector. The results show that: the horizontal movement of the blast deflector caused by the sea launch ship significantly increases the total pressure on the deflector surface, with a maximal increase of 70% under some operating conditions; as the rotation angle of the blast deflector increases, the total pressure of the deflector surface increases; the specific combination of the movement will cause local high temperature and pressure in the blast deflector. The research results can be used as a reference for the configuration design and thermal protection of the blast deflector for the sea launch of the carrier rocket.