The performance of coke in blast furnace (BF) used to prefer a high strength and low reactivity, generally, while the high reactivity coke commonly has a low strength. To overcome the contradiction, we are going to use the catalytic effect on the coke gasification. It is important to clarify the mechanism of coke gasification concerning to the coke microstructure and pore. In this study, the coke gasification was analyzed using μ-X-ray CT (Computed Tomography). The optimum conditions for the image processing of the data from the X-ray CT were obtained through the comparison with the cross section of the coke embedded in a resin. Nondestructive observation became possible. To improve resolution of the nondestructive observation, the sample shape was changed from spherical to cylindrical one and the observation conditions were adjusted to an optimum one. It was found that the resolution of the nondestructive observation of cylindrical sample was better than that of spherical sample. Using high precision μ-X-ray CT, the position of the catalyst added and the reaction behavior became clear. Furthermore, using new developed image processing of the data from the μ-X-ray CT, macroscopic reaction behavior of the catalyst became clear.