In order to improve the cycle performance of LiMn2O4, the modified LiMn2O4 was prepared by solid-state reactions using LiMn2O4 and LiCoO2 as precursors. XRD and EDS were used to study the structure properties of the modified LiMn2O4. The electrochemical properties of the modified LiMn2O4 were also investigated. The results show that Li and Co atoms could insert into the LiMn2O4 crystal lattice and a newly formed spinel phase, modified LiMn2O4 was obtained. The modified LiMn2O4 exhibits excellent cycle ability at room and elevated temperatures compared to pure LiMn2O4. The improved electrochemical stability of the modified LiMn2O4 attributes to the entrance of Li and Co ions inserted into the spinel crystal structure.