Like using “weight set” to calibrate scale, the measurement of illite crystallinity (IC) needs the same kind of “weight set” to calibrate the X-ray diffractometer too. This leads the IC measurement go smoothly and make it comparable internationally. This “weight set” is called IC standards or international IC set. The 2nd Kübler-Frey international symposium hold a round table meeting to discuss the problems about the illite crystallinity standardization including the international IC set and the boundaries of anchizone. It is unanimously agreed that to calibrate the illite crystallinity Kübler index it is important and essential to use international IC set, and that any publish with IC data without calibrated with international IC set will be rejected. Only those calibrated with international IC set can be used to determine the anchizone in a level of comparable internationally. This study discusses these problems arising within illite crystallinity measurement including instrumental type and difference, alignment situation, measuring conditions, sample conditions and calibration technique etc.