The composite materials of Ni-applied, porous zirconia balls with molten Na2CO3 salt were examined for use in solar thermochemical reforming of methane as the catalyst with high-temperature thermal storage. The millimeter-sized composite balls were tested on the heat discharge property and the catalytic activity for CO2 reforming of methane in a laboratory-scale reactor The high heat capacity and large latent heat (heat of solidification) of the composite molten salt circumvented the temperature dropping of the catalyst bed, which resulted in the alleviation of rapid decay in chemical conversion during cooling mode of the reactor The composite catalyst is expected to realize stable operation in the solar reformer under fluctuation of insolation by a cloud passage.