Disclosed are a core/shell catalyst for ethanol synthesis, a preparation method therefor and the use thereof. The catalyst comprises: (A) 40-80 weight% of a copper-based catalyst core containing CuMaOx of formula (I); and (B) a molecular sieve catalyst shell. The preparation method comprises: impregnating the copper-based catalyst particles with a silica sol, and cladding the particles with the molecular sieve catalyst; or subjecting a silane coupling agent solution and the copper-based catalyst particles to a hydrothermal treatment, then subjecting same and a pure silicon molecular sieve to a hydrothermal treatment, and finally, subjecting the resulting calcined product to a hydrothermal treatment with the molecular sieve catalyst. By means of the method, not only is the core/shell catalyst conveniently and successfully prepared, but an improved conversion rate of dimethyl ether and improved ethanol selectivity are also obtained when the catalyst is used for preparing ethanol from dimethyl ether and a synthesis gas by means of a one-step method.