Series of Co-Al and Co-Cu-Al hydrotalcites were synthesized, thermally activated and characterized. The correlation between the hydrotalcite composition and their IR spectra were discussed along with the results of X-ray diffraction analyses. The specific surface areas of hydrotalcites and their catalytic activities for nitrous oxide decomposition upon calcination were studied. As Co was partially replaced by Cu. the catalytic activity was improved by 10% under the same reaction conditions (Co/Cu/Al = 2.7/0.3/1). A spinel CuxCo3-xO4was formed in calcined hydrotalcites.