MnO2 is widely used in electrocatalysis, electrochemical energy storage, biomedicine, and electrochromic devices, due to its advantages of abundant resources, low cost, and excellent electrochemical performance. This review summarizes the latest advances in applying MnO2 as electrocatalysts for oxygen evolution, hydrogen evolution, nitrogen reduction, urea oxidation, carbon dioxide reduction, and alcohol oxidation. The structural characteristics and synthetic methods of MnO2 are summarized. Then, the structure-activity relationship between the crystal shape, microstructure, electronic structure, and catalytic performance is systematically analyzed, and its application in constructing high-efficient catalytic electrode materials and performance optimization strategy are also discussed. Finally, the development direction of MnO2-based catalytic electrode materials is prospected based on the existing problems.