The insertion/removal processes of lithium ion in chromium doped spinel lithium manganese oxide (LiCr x Mn2−x O4) were studied with electrochemical impedance spectroscopy (EIS) on a powder microelectrode, as well as X-ray diffraction (XRD) and cyclic voltammetry (CV), and was compared with those of pure spinel lithium manganese oxide (LiMn2O4). The insertion/removal process of lithium ion in the spinel oxides consists of three steps: charge transfer of lithium ion on the surface of the spinel oxides, diffusion and occupation of lithium ion in the lattice of the spinel oxide. The doping of chromium in spinel lithium manganese oxide results in the increase of the charge transfer resistance and the double layer capacitance for lithium insertion or removal and the decrease of the diffusion coefficient of lithium ion in the lattice of spinel oxide. However, the insertion capacitance, a parameter reflecting the occupation of lithium ion in the lattice of the spinel oxide, is hardly influenced by the doping of chromium. The influence of the doped chromium on the kinetic process of lithium insertion/removal in spinel lithium manganese oxide is related to the contraction of spinel lattice due to the doping.