An iteration method in the energy calibration of AES has been developed by using elastically backscattered primary electrons with possibility of 15 meV (σ) for the energy range from 10 eV to 1200 eV, in which our improved novel prototype cylindrical mirror analyzer (CMA) has been used. For the true kinetic energy calibration, the relative work function of sample to CMA was investigated by changing sample bias to CMA at ground level. It can be obtained by observing the onset of secondary electrons (SE) since SE are believed to begin just above “0” of vacuum level, although it is hardly possible to obtain a true spectrum.