The invention relates to a preparation method and application of a micro-nanostructured iron oxide/carbon composite material. The iron oxide/carbon composite material synthesized by adopting a hydrothermal method and subsequent heat treatment has a micro-nano porous core-shell structure, and the carbon shell layer can effectively enhance the electron transport of an iron oxide material and alleviates the volume expansion problem of the iron oxide material in a process of electrochemical cycle at the same time, so that a higher specific capacity and stable cycle performance can be finally obtained; the micro-nanostructured iron oxide/carbon composite material is an ideal lithium ion battery negative material, and can be widely applied to lithium ion power batteries requiring high energy density, long service life and high stability. Furthermore, the preparation method provided by the invention is simple, easy in control of conditions, low in cost, low in requirements for equipment, andconvenient for mass production, thus having a good application prospect.