An olefin conversion catalyst and its preparation method and application are disclosed. The catalyst comprises the following components, in parts by mass: a) 50-90 parts of a molecular sieve with a structure of twelve-membered ring and above; b) calculated as oxide, 0.1-10 parts of an added component selected from Group IA metal elements, Group IIA metal elements, or a combination thereof; c) calculated as oxide, 0.1-10 parts of a modifying component selected from silicon, germanium, bismuth, tin, boron, gallium or a combination thereof; and d) 10-49 parts of a support component. When the catalyst is used to convert a small amount of olefins in an aromatic distillate oil, it has the characteristics of high activity and stability, long life and effective utilization of olefins.