Abstract: We simulated radiation ablating Aluminum foil by using 1D muti-groups code(RDMG). With intense laser beams heating a gold hohlraum, the X-ray with intensity of 0.71 1014W× cm- 2 and pulse width 1.0ns emits from the hohlraum ablating 1.5m m and 3m m thick aluminum foil. The simulation investigates the radiation energy transport in hot dense mdium-Z matter (aluminum) and clearly shows the process of radiation heat wave passing through the aluminum foil. It has shown the sudden onset of X-ray flux from rear side of aluminum foil observed by experiments. The burn-through times predicted by the simulation fit well with the experimental results.