The invention discloses a preparation method of an iron oxide dodecahedron nanocrystal catalyst with an exposed high-index surface. The preparation method comprises the following steps: firstly synthesizing iron oxide cubes, then engraving the pre-synthesized iron oxide cubes with different morphologies by using different acids as chemical engraving agents, carrying out secondary modification on the morphologies of the iron oxide cubes, and introducing an extremely special crystal face {1010} face into the nano-particles. When the morphologies, sizes, etching time and the like of mother crystals are different, the obtained nano-particles have different morphologies. Two strategies of bottom-to-top and top-to-bottom are combined to regulate the morphology of iron oxide. The two strategies are common strategies in synthesis, crystal growth is controlled on the basis of thermodynamically favorable directions in the two strategies in order to obtain the iron oxide nanocrystal with the mainly exposed {1010} surface, and the obtained nanocrystal has a uniform morphology and excellent electrochemical performances.