Mesoporous NiO–Al2O3 catalysts were applied to catalytic partial oxidation of methane at 650 °C, 1 MPa with a feed composition of CH4/O2/N2/Ar = 5.2 vol.%/2.6 vol.%/4.9 vol.%/balance. In order to investigate the effect of mesopore of the catalyst on the catalytic activity, we used various types of organic reagents, such as P123, F127, PEG6000, and some carboxylic acids, to prepare bulk NiO–Al2O3 catalysts. Among the organic reagents P123, F127, and PEG6000 were effective for the formation of mesopores.