The grain characteristics of four kinds of ZrO2 nanocrystalline powders were manifested and discussed in this paper. The grain size of sample 1 tested by XRD, TEM and BET is consistent. The agglomeration coefficient of Sample 1 is higher, about 62.5, and the span of grain distribution is 14.58. The grain sizes of Sample 2 and 3 tested by XRD, TEM and BET are different. These differences identify the crystalline domain including 2~3 unite, which make the departure spheres in TEM. There are more soft agglomerates in Sample 2 with the agglomeration coefficient of 25.71 and the span of grain distribution being 18.94 than that in Sample 3 with the agglomeration coefficient of 6.89 and the span of grain distribution being 8.91. The grain sizes of Sample 4 tested by XRD, TEM and BET are obviously different. That identifies the large hard agglomerates.