Abstract: Nano-sized MnO₂ was synthesized by loading KMnO₄ on a mesoporous silica KIT-6 template and calcination at different temperatures (400-700℃). The microstructure and electrochemical performance of nano-sized MnO₂ at different calination temperatures were studied. The results show that the prepared nano-sized MnO₂ was composed of δ-MnO₂ with layered structure when calcined at 400℃, δ-MnO₂ with layered structure and a small amount of α-MnO₂ with tunnel structure when calcined at 500℃, α-MnO₂ with tunnel structure which presented ordered mesoporous morphology and rod shape morphology, respectively, when calcined at 600℃ and 700℃. The α-MnO₂ with tunnel structure showed a better cycling stability than that of δ-MnO₂ with layered structure, and had a discharge capacity more than 100 mAh·g^-1 after 50 cycles of charge-discharge at a current density of 100 mA·g^-1.