According to first principle simulations,we theoretically predict a type of stable single-layer graphene oxide (C2O).Using density functional theory (DFT),C2O is found to be a direct gap semiconductor.In addition,we obtain the absorption spectra of the periodic structure of C2O,which show optical anisotropy.To study the optical properties of C2O nanostructures,time-dependent density functional theory (TDDFT) is used.The C2O nanostructure has a strong absorption near 7 eV when the incident light polarizes along the armchair-edge.Besides,we find that the optical properties can be controlled by the edge configuration and the size of the C2O nanostructure.With the elongation strain increasing,the range of light absorption becomes wider and there is a red shift of absorption spectrum.