Single phase chromium-substituted orthorhombic LiMn1-xCrxO2 (0≤x≤0.05) were successfully synthesized by hydrothermal treatment of Mn2O3, Cr2O3 and lithium hydroxide aqueous solution. Structure and morphologies of the o-LiMn1-xCrxO2 were characterized by X-ray diffraction and transmission electron microscopy.Compared to the particle size of o-LiMnO2 ranging from 50 to 150 nm, the Cr-doped one is larger with about 500 nm, which is agglomerated by small grains. There are high stacking faults in nanosized grains that cause easier phase transformation from the orthorhombic to the spinel-like structure on cycling. High-resolution transmission electron microscopy image analysis of electrochemically cycled o-LiMn1-xCrxO2 (x=0, 0.05)samples showed that the nanodomain structure in o-LiMn0.95Cr0.05O2 was comparatively perfect to that in o-LiMnO2. Particle agglomeration and the relatively perfect crystal structure are two key factors for improving cycle performance of o-LiMn0.95Cr0.05O2. The obtained o-LiMn0.95Cr0.05O2 can reach a maximum discharge capacity of 174 mA·h·g-1 at 0.1 C rate in seventh cycle. The discharge capacity fade rate of the samples decreased with increasing Cr amount. Furthermore, o-LiMn0.95Cr0.05O2 gives a highest discharge capacity of 150 mA·h·g-1 at a high current rate of 0.5 C, and retains 130 mA·h·g-1 after 40 cycles.