Some compounds of LiCo1-xRExO2 (RE=rare earth elements and x=0.01～0.03) were prepared by doping rare earth elements to LiCoO2 via solid state synthesis. The microstructure characteristics of the LiCo1-xRExO2 were investigated by XRD. It was found that the lattice parameters c are increased and the lattice volumes are enlarged compared to that of LiCoO2. Moreover, the performance of LiCo1-xRExO2 as the cathode material in lithium ion battery is improved, especially LiCo1-xYxO2 and LiCo1-xLaxO2. The initial charge/discharge capacities of LiCo0.99Y0.01O2 and LiCo0.99La0.01O2 are 174/154 (mAh*g-1) and 159/149 (mAh*g-1) respectively, while those for LiCoO2 working in the same way are only 139/131 (mAh*g-1).