Operating characteristics of a gas membrane separation process were described qualitatively. Various methods of controlling the permeate gas flux were compared. One optimal method of auto-controlling the permeate gas flux was applied for the first time. The permeate gas flux could be auto-controlled through a control valve installed on the residue gas line. The correctness and the effectiveness of control philosophy were verified successfully in the process of extracting high purity hydrogen from a continuous reformer in Luoyang Petrochemical Refinery of China. Therefore, operation of membrane separation equipment was optimized. Operational flexibility and adaptability of membrane separation equipment were enhanced further. The method is the same with all flux control of permeate gas as product gas. This paper also makes suggestions for further investigation. (c) 2006 Elsevier B.V. All rights reserved.