Abstract: In view of the current situation of lacking diagnostic level dosimeter calibrating unit, a standard radiation condition composed of X-ray equipment, positioning device, temperature measuring instrument and barometric pressure measuring instrument was provided, thus building the standard condition for the calibration of diagnostic level dosimeter. The uncertainty of this radiation condition was evaluated as U= 3. 8% (k= 2) by measuring and analyzing the air kerma of the radiation field. This standard radiation condition can meet the calibration of diagnostic level dosimeter.