For the separation of an ethylene/ethane mixture, a novel copper(I)-based supported ionic liquid membrane (SILM) with high permeability has been fabricated. This SILM was prepared from a polyvinylidene fluoride microporous membrane impregnating the copper(I) based IL which formed by the cuprous chloride (CuCl) and 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]). Scanning electron microscopy, attenuated total reflection Fourier transform infrared spectroscopy, and time of flight mass spectroscopy were used to characterize the SILM. Pure and mixed gas permeation experiments were carried out to investigate the influences of ILs composition, trans membrane pressure, temperature, and time upon the separation performance. This SILM showed comparable C2H4 permselectivity but outstanding permeability with a long-term stability beyond the reported polymeric membrane upper bound. At the CuCl/[Bmim] [Cl] ratio of 2, the C2H4 permeability and permselectivity reached 2653 barrer and 11.8, respectively. Furthermore, the facilitated transport effect was studied by H-1 NMR and quantum mechanical calculations. The anionic species formed by sp hybridization of Cu+ possesses unfilled attachment sites to selectively complex with C2H4 and weaken the interionic hydrogen bond of [Bmim] [Cl], thus lowering the system's viscosity.