Abstract: This experiment was conducted to explore the pathogenicity variance of Cryptosporidium baileyi isolates derived from different poultry hosts in quails. The chickenderived, duckderived, quailderived, White Java sparrowderived, and ostrichderived C. baileyi isolates were inoculated to 10dayold quails respectively and the pathogenicity was observed by microscopy and scanning electron microscopy (SEM) techniques. Diarrhea and the symptom of respiratory passage were shown, and the patent period of oocyst shedding was 1118 days. The development stages were found to localize in the throat, trachea, bursa of Fabricius and cloacal chamber. In the duckderived C. baileyi infected group, the morbidity and mortality were 82.5% and 25%, respectively. Likewise, the morbidity and mortality were 77.5% and 12.5% in Zhengzhou chickenorigin C. baileyi infected group, 37.5% and 17.5% for the quailorigin infected group. The present results suggest that there was pathogenicity variance in quails using C.baileyi isolates derived from different hosts, and the intensity of pathogenicity variance was corresponding to different C. baileyi isolates.