The invention provides a three-dimensional ordered macroporous alumina and a preparation method thereof, wherein the method comprises the following steps of: assembling polymer microspheres which are singly dispersed to form a colloidal crystal template, filling the alumina sol which is prepared by means of a special method into the template, and drying and roasting to obtain macroporous alumina.The method provided by the invention has the advantages that the alumina sol and the compounding process of the alumina sol and the polymer microspheres can be controlled well, the network structure of the alumina sol is protected possibly, the alumina which is prepared by means of the method not only has three-dimensional ordered macroporous channels but also has a high specific surface area. Furthermore, the macropores within the material are communicated to the surrounding macropores by means of 12 small window holes, and the window holes are formed by sintering the template properly. The alumina prepared by means of the method provided by the invention is suitable for being used as a catalyst carrier of heavy oil and an adsorption and separation material of organic macromolecule. The alumina prepared by means of the method which is provided by the invention is suitable for improving the mass transfer capability of the material within the catalyst and is suitable for improving the activity and the selectivity of the catalyst during the application process as a catalyst carrier.