A NiP-Cu multi-layer composite membrane was prepared by an improved technique of electroless plating with metal-activation paste and applied to membrane reactor of ethanol dehydrogenation. The results showed that the yields of acetaldehyde observed over a NiP-Cu composite membrane reactor were obviously higher than those observed over a Ni-P membrane reactor due to catalytic activity of NiP-Cu membrane itself. Meanwhile the effect of the reaction temperature, sweeping argon rate and space time, W/F, on the ethanol conversion and the selectivity of acetaldehyde are investigated, and the mechanism of catalytic dehydrogenation for ethanol going through NiP-Cu composite membrane was analyzed. The surface morphology and bulk structure of NiP-Cu composite membrane were characterized by means of technique such as SEM and XRD. (C) 2003 Published by Elsevier Science B.V.