Thin palladium composite membranes were prepared by modified electroless plating method on a-alumina supports and a dense Pd/alpha-Al2O3 composite membrane with high hydrogen flux, good selectivity for hydrogen was obtained. It was tested in a single gas permeation system for hydrogen permeance and hydrogen selectivity over nitrogen. The hydrogen permeance of the corresponding membrane was as high as 2.45X10(-6)mol center dot m(-2)center dot S-1 center dot Pa-1 and H-2/N-2 selectivity over 700 at 623K and a pressure difference of 0.1MPa. The main resistance of the composite membrane to H-2 permeation lies in the aluminum ceramic support rather than the thin Pd layer.