The indium- and sulfur-doped LiMnO2 samples with orthorhombic structure as cathode materials for Li-ion batteries are synthesized via hydrothermal method. The microstructure and composition of the samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma atom emission spectroscopy (ICP-AES), and X-ray photoelectron spectroscopy (XPS) analysis. It is shown that these samples with the orthorhombic structure have irregular shapes with a grain size of about 100–200nm. The electrochemical performance of these samples as cathode materials was studied by galvanostatic method. All doped materials can offer improved cycling stability and high rate discharge ability as compared with the un-doped Li0.99MnO2. Moreover, dual In/S doping can slow down the capacity decay to a great extent, although the transformation to spinel occurs undesirably for all the doped samples during electrochemical cycling.