The present invention provides a method for the adsorptive separation of C2H4 and C2H6 using ultramicroporous metal-organic framework material, comprising the following steps that (1) C2H4/C2H6 mixture is contacted with the ultramicroporous metal-organic framework material; (2) C2H4 is preferentially adsorbed and the separation of C2H4/C2H6 is realized. The described “ultramicroporous metal-organic framework material” has a formula of [M3L3A]∞, wherein M represents the metal cation being any one of Cu2+, Zn2+, Co2+, and Ni2+; L represents the organic linker being any one of 1,2,4-triazole and its derivatives; A represents the oxygen-containing inorganic anion being any one of PO43− and VO43−. The class of ultramicroporous metal-organic frameworks has optimal pore size and pore chemistry, exhibiting both higher uptake capacity and faster adsorption rate for C2H4 as compared to C2H6, thus C2H4 can be preferentially adsorbed by these metal-organic frameworks with high selectivity, and high-purity C2H4 can be separated from C2H4/C2H6 mixtures efficiently.