Indium oxide (In2O3) coating on Pt, as an electrode of thin film lithium battery was carried out by using cathodic electrochemical synthesis in In2(SO4)3 aqueous solution and subsequently annealing at 400°C. The coated specimens were characterized by X-ray photoelectron spectroscopy (XPS) for chemical bonding, X-ray diffraction (XRD) for crystal structure, scanning electron microscopy (SEM) for surface morphology, cyclic voltammetry (CV) for electrochemical properties, and charging/discharging test for capacity variations. The In2O3 coating film composed of nano-sized particles about 40nm revealing porous structure was used as the anode of a lithium battery. During discharging, six lithium ions were firstly reacted with In2O3 to form Li2O and In, and finally the Li4.33In phase was formed between 0.7 and 0.2V, revealing the finer particles size about 15nm. The reverse reaction was a removal of Li+ from Li4.33In phase at different oxidative potentials, and the rates of which were controlled by the thermodynamics state initially and diffusion rate finally. Therefore, the total capacity was increased with decreasing current density. However, the cell delivering a stable and reversible capacity of 195mAhg−1 between 1.2 and 0.2V at 50μAcm−2 may provide a choice of negative electrode applied in thin film lithium batteries.