Abstract: Based on the field geological observation, the different kinds of "Di" of chicken-blood stones from Changhua are tested by using the means as conventional gemmological methods,XRD and IR. The results show that the quality of "Di" of chicken-blood stones from Changhua is closely related to the compositions and the content of the main mineral. The higher content of dickite and the better order degree of the structure could result in the better quality of "Di".Alunite added in the chicken-blood stones could reduce the transparency of "Di" while the hardness increases. From the "Ruan Di" to the "Gang Di", the content of alunite and quartz increases. When the content of quartz is over 25%, the "Di" of chicken-blood stones from Changhua belongs to the "Ying Di".