Activated carbon (AC) was prepared from a subbituminous coal with addition of Ca(NO3)(2) by KOH activation, and used for catalytic methane decomposition to produce hydrogen. The effects of calcium addition amount on the structure and catalytic performance of the resultant ACs were investigated. As the addition of Ca(NO3)(2), the surface area and pore volume of ACs increase significantly compared with that of AC without addition, especially the mesoporous surface area improved from 480 m(2)/g to 1119 m(2)/g. Almost hyaline structure of carbons are obtained when a high amount of calcium is added into the coal. The addition of calcium in coal leads to the significant increase of methane conversion over the resultant carbon catalysts, and when the calcium addition amount is 15 wt%, the prepared AC has the highest mesoporous surface area and the best stability. No direct relationship was found between specific surface area and the activity of carbons, but the mesopores benefit the stability of ACs in methane decomposition. Carbon fiber was produced on AC from the coal with addition of calcium compared with the aggregated carbon on that from coal without addition of calcium.