The invention discloses a catalyst for synthesizing a glimepiride key intermediate and a synthesizing method thereof. The key intermediate is 3-ethyl-4-methyl-3-pyrrolin-2-one synthesized by ethyl 2-ethyl-3-hydroxyl-3-cyanobutyrate. The catalyst takes Al2O3 as a carrier and comprises composite active component which is one or more simple substances or the simple substances and oxides of selected from Co, Ni, Cu, Cr, Fe and Zn, wherein the mass content of each active component is 1-20 percent of the total mass of the catalyst and the total content of the active components is 8-45 percent of the total mass of the catalyst. The catalyst is prepared by taking the Al2O3 as the carrier loading routine metals, is simple and convenient to prepare, low in cost and stable in activity and can be recycled. The method has the characteristics of easy control of operation conditions, good catalyst performance and high product yield.