A novel, thin (6 mum), defect-free Pd/MPSS (macroporous stainless steel) composite membrane tube was prepared by using a multidimensional plating mechanism. A high hydrogen permeation flux of 0.260 Mol/(m(2) s) and complete hydrogen selectivity were obtained at a temperature of 500 degreesC and a pressure difference of 100 kPa. The catalytic membrane reactor for steam reforming of methane was constructed with the as-synthesized thin Pd/MPSS composite membrane and a commercial Ni-Al2O3 reforming catalyst. Methane conversion, hydrogen extraction ratio, and hydrogen production rate of the membrane reactor were studied in detail under different operating parameters such as temperature, pressure, space velocity, steam-to-methane ratio, and sweep gas flux. Some important effects were found for these operating parameters to the three performance factors. Drastic superiority to the traditional reactor was proved by changing the Pd-based membrane tube to a dense stainless steel tube with the same diameter. Moreover, on comparison with the experimental results and the simulation predictions in other catalytic membrane reactors appearing in the literature, the reactor constructed in the present work had a relatively better performance, due to the higher hydrogen permeance of the thin Pd membrane and the proper operating parameters.