z Dimethyl ether (DME) steam reforming was performed in a gamma-alumina/silica/stainless steel composite membrane reactor combined with a water gas shift (WGS) reaction to achieve three important aims simultaneously, such as DME conversion improvement, high hydrogen recovery, and CO elimination. The Knudsen membrane with high permeability was used to increase conversion improvement and hydrogen recovery. In one process of the DME steam reforming membrane reactor combined with the WGS reaction, the DME conversion was improved up to 35% in comparison with a conventional reactor, and hydrogen recovery was about 20%. The CO was not detected in the permeate side of the membrane reactor. The high CO removal efficiency was obtained from the WGS reaction with the Pt/TiO2 catalyst in the permeate side of the membrane reactor.