Fluid interface instability seriously affects the performance of ICF (inertial confinement fusion) capsule implosion, doped CH plastic or Be (Beryllium) ablator is generally employed in ICF capsule. The RM(Richtmyer-Meshkov) instability occurs when the radiation-generated shock penetrates the rippled inner surface of ablator. In order to explore the resistance ability to RM instability with Be or CH plastic as ablator, theoretical analysis and numerical simulation were carried on the evolution of RM instability. Theoretical analysis indicates that the linear growth rate of RM instability depends on the radiation temperature, the wavelength，the initial amplitude of perturbation and the density of ablator. The hydrodynamics process of high temperature (above 100 eV) blackbody spectrum X-ray ablating rippled interface of Be/Foam and CH/Foam target is simulated by a radiation hydrodynamic code. Simulation results show that the Be ablator with higher density has stronger resistance ability to RM instability than CH plastic ablator. The results are useful for capsule design in inertial confinement fusion.