The invention provides a molecular sieve catalyst for preparing low-carbon olefin, and the catalyst comprises the following raw materials by parts by weight: 30-93.7 parts of Na-ZSM-5 zeolite, 5-40 parts of bonding agent, 0.1-10 parts of modifier of mixed elements, 1-15 parts of hole structure regulator and 0.1-5 parts of extrusion assistant, and the modifier of the mixed elements is a soluble substance containing one or a plurality of elements of B, P, La, Ca, Mg, Sr, Zn, Cu, Mn, Cd, Ga and In. The invention further provides a prepration method of the catalyst. The molecular sieve catalyst adopts the extrusion assistant and adds an appropriate amount of hole structure regulator, thereby improving product strength and hole structure, effectively improving diffusion performance of the catalyst and further improving selectivity of the low-carbon olefin. The catalyst has the advantages of appropriate strength, high hydrothermal stability, high activity and high selectivity of propylene.