The invention relates to an aluminium ion battery and a preparation method thereof and belongs to the field of aluminium ion batteries and preparation thereof. The aluminium ion battery comprises a positive electrode, a negative electrode and an aluminium ion electrolyte, wherein the positive electrode is made of transition metal oxide; the negative electrode is made of high purity aluminium; the battery comprises a diaphragm material when the aluminium ion electrolyte is in a liquid state. Since abundant aluminium elements are stored, the cost for the ion battery is greatly reduced; the safety performance is improved; the transition metal oxide is applicable to hypervalent ion batteries due to relative stability under the variable valence states and different valence states. The ion liquid serves as the electrolyte for the hypervalent ion battery, so that aluminium ion is high in conductivity, good in heat stability, broad in electrochemical window and high in chemical stability and almost incapable of reacting with the positive electrode materials, the negative electrode materials, a current collector, a binder and a diaphragm in a battery system and capable of maintaining the liquid state in a board temperature range. The aluminium ion battery can be applied to various fields, such as electronic industries, communication industries and electric vehicles and the like.