In the paper, the process of determining the degree of graphiti-zing of metallurgy coke with X-ray diffraction method was discussed. The extrapolation was used in order to obtain the interplanar distance. of (002) crystaloface of metallurgy coke. The finding showed that the dmax. wasn't 3.44A, butO4.31A. A rational formula which could be used to characterize the degree of gra-phitizing of metallurgy coke was found.