In this paper, we reported the synthesis of single-crystalline octahedral LiMn2O4 particles by a two-step method in which well-shaped octahedral Mn3O4 was easily obtained by the hydrothermal reaction of KMnO4 in water/N, N-dimethyl formamide (DMF) mixed solution and then transferred to LiMn2O4 by the solid-state lithiation process. High crystallinity and phase purity were also observed. When used as a cathode for Li-ion battery, the octahedral LiMn2O4 particles have demonstrated superior electrochemical properties in comparison with the LiMn2O4 particles by sol-gel method. A high initial discharge capacity of 122.7mAhg−1 was exhibited at 1C-rate and 104mAhg−1 maintained after 200 cycles for octahedral LiMn2O4. And good rate capability has also been achieved. The excellent electrochemical properties should be mainly attributed to the special octahedral morphology, single crystalline nature and high crystallinity.