Aqueous zinc ion batteries have high application value and development prospects in large-scale energy storage and other fields. Manganese dioxide has the advantages of abundant reserves, low price, safety and environmental protection, and rich crystal structure. As a cathode material for aqueous zinc-ion batteries, it exhibits excellent electrochemical characteristics and has become the most concerned type of cathode material. However, during the charging and discharging process, the crystal form of manganese dioxide is changeable and accompanied by other surface reactions, the reaction mechanism is still controversial. In the past two years, with the successive reports of several important works, the electrochemical reaction mechanism has gradually become clear. This article focuses on the characteristics of the crystal structure of manganese dioxide and its performance as a cathode for aqueous zinc-ion batteries, combined with the latest research progress, and focuses on the energy storage mechanisms of different crystalline manganese dioxide, and prospects for its future development.