The Mn modified lithiated vanadium oxides LiV3-xMnxO8 (x=0.00, 0.01, 0.02, 0.04, 0.06, 0.08, 0.10) as promising cathode materials for secondary lithium batteries were prepared using a hydrothermal method. Crystalline phases were characterized by powder X-ray diffraction (XRD) and the morphology was observed by scanning electron microscopy (SEM). The electrochemical properties of the synthesized samples were investigated by galvanostatic charge and discharge at a current density of 50 mA·g-1. The effects of manganese doping on crystal stability were analyzed in terms of the material structure and electrochemical performance. The electrochemical properties were greatly improved after manganese doping. Among the doping modified materials, LiV2.94Mn0.06O8 showed the highest initial specific discharge capacity which was 295 mAh·g-1. od cycle performance was achieved when 0.01≤x≤0.08. All the LiV3-xMnxO8 (0.01≤x≤0.08) materials maintained the specific discharge capacities of more than 120 mAh·g-1 after 20 cycles and 100 mAh·g-1 after 40 cycles thereby preserving the high charge-discharge efficiencies of no less than 93%.