The invention relates to a catalyst for a reaction for preparing 1,3-butadiene from ethanol, a preparation method and applications thereof. The catalyst is an MFI type molecular sieve, which has a nanosheet layer structure, contains two transition metals X and Y and an alkaline earth metal Z, and is formed by cross growth of nanosheet layers, wherein the thickness of the nanosheet layer is 2-50 nm, the metal component X of the catalyst is one or more than two selected from transition metal elements Zn, Ni, Fe, Cu and Ag, the component Y of the catalyst is one or more than two selected from acidic or alkaline metals Zr, Y, Hf, La, Ce, Sn and Ta, and the metal elements are loaded on a molecular sieve carrier in a post-treatment manner. The invention provides a catalyst for preparing 1,3-butadiene by stably and efficiently catalyzing ethanol conversion, a preparation method and applications thereof, wherein the catalyst has obvious industrial application value in a process for preparing butadiene from ethanol.