Influence of charge coupled device (CCD)′ s nonlinear response characteristics on the near-field and far-field beam quality′ s measurement of high power laser system is analyzed. A new calibration method, based on single slit diffraction, is presented to calibrate CCD′ s photoelectric characteristics. Accomplish the calibration of a given CCD and restore the grey level of near-field and far-field energy distribution by the calibration curve in ideal and practical system to observe the influence on the measurement of near-field fill factor (FF) and far-field encircled energy distribution. The restoration shows that in a certain laser system the near-field FF will improve 1% ~2% after the grey level restoration. And it has nearly no influence on the farfield energy distribution parameters.