Abstract: The total response of sub-kilovolt x-ray energy spectrometer was calibrated on the high intensitity charged ion-induced x-ray source facility.The absolutely calibrated values of the sensitivity of XRD (Al) and reflectivity of Ni mirror(5°) were given. The results were compared with experimental and theoretic results of of R.L.Kauffan's and B.L.Henke's research works.