Morphometrical analysis of chicken Crytosporidium baileyi in various stages of life cycle in the bursa of Fabricius wer carried out by electron microscope to establish a differential point for identification of C baileyi. By avidin-biotin complex method, protozoans of the bursa of Favricius were identified Cryptosporidium spp. The size and area on each developmental stages of C baileyi, as measured by Morphomat 10 attached to electron microscope were as follews. Trophozoites' size with range of 3.21+_0.70*2.49+_0.59 micro meter, area with range of 118. 82+_41.92 micro meter2; meronts' size with 3.99+_1.07*2.96+_0.52 micro meter, area 210.11+_57.11 micro meter2 ; merozoites' size 1.98+_0.43*0.60+_0.18 micro meter, area 24.10+_5.97 micro meter2; microgametes' size 1.36+_0.83*0.50+_0.23 micro meter, area 20.23+_6.73 micro meter2; macrogametes'size 4.57+_0.65*4.02+_0.55 micro meter, area 258.37+_51.83 micro meter2; oocytes' size 4.39+_0.56*3.44+_0.50 micro meter, area 187.21 +_62.68 micro meter2. In conclusion, the size and area on each developmental stages of Cryptosporidium baileyi is different from that of other Cryptosporidia spp. It suggests, with considering tissue tropism and life cycle, morphometrical analysis can be quite a good way to identify C baileyi.