Variable nozzle has converging and diverging flap. So it has advantage to change variable cross section area of nozzle throat. Additionally, it can able to control by actuators in nozzle system. This nozzle system operates at high temperature, speed and pressure. Therefore, it is very important to consider structural safety of the nozzle design. Also, if the area of nozzle throat is changed, pressure and temperature fields are also varies. Hence, the interaction analysis between CFD(Computational Fluid Dynamics) and FMBD(Flexible Multi-Body Dynamics) is must be required. In this paper, a study on the variable nozzle system is conducted using CFD-FMBD interaction analysis on environments of high temperature and pressure.