Abstract: In this work, a series of CuNH₄Y-x zeolite adsorbents were prepared by ion exchange with different concentrations of CuCl₂ and NH₄Y zeolite. The effects of the valence and loading of Cu on the adsorption and separation of ethylene and ethane were investigated by fixed bed breakthrough adsorption experiment based on a series of characterization methods. The results of breakthrough adsorption experiments show that the ethylene adsorption capacity of Cu(I)NH₄Y_0.10 is significantly higher than that of Cu(II)NH₄Y_0.10, and the ethylene adsorption capacity of Cu(I)NH₄Y series adsorbents increases first and then decreases with the increase of loading of Cu species. H₂-TPR and HRTEM results show that monatomic Cu(I) species in the supercages of zeolite Y should be the effective active site when the loading amount of Cu is low. With the increase of Cu loading amount, the aggregation of Cu species results in the reduction of adsorption capacity of ethylene. The results of DFT calculation also confirm that the ethylene adsorption capacity of Cu(I)NH₄Y adsorbent is significantly stronger than that of Cu(II)NH₄Y adsorbent. These results can provide important theoretical basis and guidance for the development of high-efficiency Cu ion modified zeolite adsorbent for ethylene separation.