Copper, aluminum-based composite metal oxides was prepd. by copptn. method and as the catalyst in synthesis of the N-methylpiperazine while the starting materials are diethanolamine and methylamine.  Compared the activity of the catalysts in autoclave and found that copper, aluminum and nickel composite metal oxides has the highest activity.  The molar ratio of copper, aluminum and nickel, different coprecipitators, precipitants order and the calcining temp. have been optimized.  Experimented results showed that: the ideal molar ratio of copper, aluminum and nickel is 1 : 1 : 3.2, coprecipitator is NaOH, precipitants order is cocurrent, and the best calcining temp. lies around