The invention discloses a preparation method of a positive material for an aluminium-ion secondary battery and application in the aluminium-ion secondary battery, and belongs to the technical field of electrochemical materials. The preparation method comprises the following steps of: adopting a pure molybdenum sheet as the material, adopting a high-temperature heat treatment method in a tubular furnace and obtaining a nano MoO2 particle material growing on the surface of the molybdenum sheet. The positive material disclosed by the invention shows excellent electrochemical property as a positive electrode of the aluminium-ion secondary battery, and the discharging voltage of the battery is 1.9V, so that the positive material can be widely applied in the fields of portable electronic equipment and new energy. The positive material, the preparation method and the application disclosed by the invention have the advantages that the process is simple, the cost is low, the product property is stable and large-scale production can be achieved.