A series of ammonia-modified multi-walled carbon nanotubes was prepared via hydrothermal method.Their catalytic activity was evaluated by oxalic acid degradation in aqueous solution in the presence of ozone.It was found that the reaction process can be fitted to zero-order reaction kinetics.The apparent zero-order rate constant had a positive relation with the basic groups and pH value at zero charge point(pHPZC)of the catalysts.On this basis，it can be concluded that the significant enhancement of oxalic acid degradation is achieved by hydrothermal treatment with ammonia.The reason could be that the method promotes formation of basic groups and increase of pHPZC.