Na0.74(Li1/3Mn2/3)xCo1-xO2 (x=0, 1/6, 1/3, 1/2) as sodium-ion battery cathode materials are prepared by using sol-gel method. The XRD tests demonstrate that Na0.74CoO2 and its Li1/3Mn2/3-substituted samples possess typical P2 structure. The charging/discharging tests exhibit that the Na0.74CoO2 electrode has a reversible capacity of 131mAhg−1 with good cycling performance. When Co is partially substituted by Li1/3Mn2/3, the Li1/3Mn2/3-substituted samples exhibit decreasing reversible capacity of 122, 115, 83mAhg−1 for x=1/6, 1/3, 1/2, respectively. However, the rate capability of the Li1/3Mn2/3-substituted samples is greatly improved due to the suppression of the complicated phase conversion in intercalation process. Moreover, the structure stability for Li1/3Mn2/3-substituted samples is apparently observed when cycled between 4.5 and 2.0V. Therefore, the substitution of Li1/3Mn2/3 can suppress the complex phase changes of the Na-based oxides and improve their electrochemical performance, which can provide a promising choose for high-performance Na-ion storage cathode material.