[en] A radiation hydrodynamic model of the atmosphere in the fusion chamber of Z-FFR is built by MULTI, and the physical processes in the atmosphere such as the X-ray radiation transport, gas temperature and density evolutions, as well as shock wave generating and propagating, are studied. Radiative temperature and impact pressure on surface of the first wall are subsequently obtained. Static calculations of the X-ray deposition in tungsten and the X-ray attenuation in the Ar atmosphere are accomplished by a Geant4 code. Combining the dynamic and static calculations, preliminary design of the fusion X-ray mitigation is accomplished. The X-ray fluence threshold incident on surface of the first wall is determined to be 0.2 J/cm², and the initial pressure of the Ar atmosphere is 2000 Pa. (authors)