In the pyrolysis process, tar material may cause operational problems, such as pipe plugging, condensation, and tar aerosol formation. An unusual approach should be introduced to solve carbon, deposition over a catalyst, which was a serious problem in the tar decomposition process. The kinetic analysis was evaluated in detail by the proposed system, tar decomposition over a porous catalyst of iron ore. Decomposition of lignite tar exhibited similar profiles of H-2 and CO generation, which was rising shortly at the beginning of the reaction because the ore catalyst still owned high activity and there was no carbon poisoning. However, the excessive carbon deposition also occurred simultaneously. Both the kinetic constant and deactivation factor were evaluated successfully using a simple proposed model with ranges of 0.1275-0.5523 and 1.7206-2.5310 s(-1), respectively, at 500-700 degrees C. The activation energy was also calculated on the basis of the Arrhenius equation, which was 44.86 kJ/mol. The deactivation factor exhibited a similar tendency with the amount of carbon deposition within pores of iron ore. It means that the carbon deposition within pores of ore was highly affected by catalyt activity. However, the high carbon content within an inactive ore catalyst offered an extra benefit in the steel production as raw material. Therefore, the tar decomposition over a porous iron ore was a promising catalyst, which was a cheap and abundant natural resource. In addition, this proposed system also offered a solution for problems related to the raw material, energy, and environment in the ironmaking industry.