Hydrogen was separated from hydrogen/nitrogen/carbon dioxide mixture gas by electrochemical method using proton exchange membrane. Separation characteristics, product hydrogen purity and power efficiencies were obtained under different operating cell temperatures and feed pressures. The purity of hydrogen was enhanced using two-staged separation process, and the permeation of nitrogen and carbon dioxide was studied. Cell characteristic, hydrogen purity, flux and efficiencies was increased as cell temperature was raised. The increase of feed pressure caused rising of flux and efficiencies, but dropped hydrogen purity. In all cases, power efficiency had the maximum value at 300 mA/cm(2). high purity, 97.39%, can be achieved from low purity feed, 33%, through two-staged separation process at 100 mA/cm(2). The permeability of carbon dioxide was larger than that of nitrogen, so the purity of hydrogen was more affected by carbon dioxide than by nitrogen.