KMn8O16 nanorods were prepared for the first time by a rheological phase reaction method, using KMnO4 and Mn(CH3COO)2·4H2O as reactants. The KMn8O16 samples annealed at different temperatures were characterized by X-ray diffraction, transmission electron microscopy, and galvanostatic charge/discharge profile measurement. The KMn8O16 nanorods annealed at 400°C show the highest reversible discharge capacity (153.8mAh/g even after 50 cycles) at current density of 50mA/g and the best cycling stability. The annealed nanorods exhibit the superior electrochemical performances compared to the unannealed sample, which is confirmed by the AC impedance measurements. These results indicate that the KMn8O16 nanorods could be a promising cathode material for lithium ion batteries.