Fourier-transform infrared (FTIR) spectra of nanometer SnO anodes at different charge/discharge states in lithium rechargeable batteries were recorded. Solvent decomposition reaction that generally presents on the surface of carbon or alkali metal is also presented on SnO anode. The surface film is composed of Li2CO3 and ROCO2Li. In addition, FTIR data indicates that absorption bands of ROCO2Li are changed below 0.7V, which is believed to be related to the change of the surface layer of SnO anode around 0.7V versus Li/Li+ during the first discharge process.