A new amorphous Ni-B alloy membrane was prepared by a modified electroless plating method. It was characterized by scanning electron microscopy (SEM), in situ X-ray diffraction (XRD) patterns, differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma (ICP). The ideal separation factor for H-2/Ar through the membrane was also measured to evaluate its separation efficiency for hydrogen. The amorphous membrane was employed as a membrane reactor for ethanol dehydrogenation and exhibited a significant promotion effect for this reaction, due to its catalytic activity as well as its high permselectivity for hydrogen.