We present a realistic and efficient scheme for sub-half-wavelength atom localization.This scheme is based on the phase-dependent elecaromagnetically induced transparency in a four-level system in the double-Λ configuration.We use a strong bichromatic field(one component of which is standing-wave field)as the driving components,and a weak bichromatic field as the probe components.By choosing the collective phase of the four applied components,the atom js localized in either of the two half-wavelength regions with 50% detecting probability when the absorption to the probe fields is detected.