Abstract: A palladium alloy membrane separator was designed to further develop its separation performance between H₂ and D₂. The separation factor of the single stage was affected by the temperature, the feed gas component, the split ratio and the gas flow rate, etc. The H₂-D₂ separation factor decreases with the increasing of temperature and decreases with the increasing of split ratio. In the range of 573～723 K, when the feed rate was 5 L/min, the separation factor of 66.2%H₂ -33.8%D₂ decreases from 2.09 to 1.85 when the split ratio was 0.1 and from 1.74 to 1.52 when the split ratio was 0.2. At 573 K and the feed rate of 5 L/min, the separation factor of 15.0%H₂-85.0%D₂ decreases from 2.43 to 1.35 with the increasing of split ratio from 0.050 to 0.534，and for 66.2%H2-33.8%D₂, the separation factor decreases from 2.87 to 1.30 with the increasing of split ratio from 0.050 to 0.688. When the separation factor is the biggest, the flow rate of feed gas is in a perfect value. To gain a best separation performance，perfect flow rate, lower temperature and reflux ratio should be chosen.