Abstract: Theoretical analysis of separation process for enriching nitrogen from air using hollow fiber membranes showed the effects of various operation parameters and membrane performance on separation results. By varying the operation conditions, nitrogen-rich gases with concentrations of 85-99.6% (vol. )were obtained, while the recovery wasbetween 78-23%. A counter-current plug model and ;) mixing plug model were verified by comparing the calculated results with the experimental data. Both models can satisfy the needs of industrial simulation and design calculation.