Carbon dioxide and hydrogen adsorptions on the Ni-CaO catalyst have been investigated using temperature-programmed desorption technique under ultra-high vacuum condition. The CaO made fromcalcium acetate and citric acid has higher surface area with mote mesopore than that made fromcalcium acetate only. The main factor giving these differences was carbon because the amounts of desorbed CO₂ from both surfaces were almost asme. With the increase of Ni loading, the CO₂ desorption temperature increased suggesting the increase of basic strength ofthe catalyst. Because of the interaction between Ni and CaO, H₂ adsorbed on Ni-CaO desorbed at higher temperature than thatadsorbed on nickel only catalyst.