Abstract:  Six hundred and eighty-six fresh fecal specimens were collected from outpatients（663 well-formed feces and 23 watery feces） during March 2011 to March 2012. All specimens were examined microscopically by direct smear and iodine stained method. B. hominis obtained from the human positive fecal specimens were cultured in LES medium, and inoculated into the abdominal cavity of 10 female mice of 6-8-week old. The abdominal fluid was examined with same methods. 103 of 686 patients were positive （80 well-formed feces and 23 watery feces）. Micro-scopically, the granular form and vacuolated form of B. hominis trophozoites could be easily identified by direct smear and iodine staining in well-formed fecal specimens, showing ovoid in shape and about（13.2±0.2） μm in size. The tro-phozoites cultured in LES medium showed similar feature. But in the watery fecal specimens and mice ascites specimen, they were amorphous containing more granules. And their average size was（28.0±0.3） μm which was larger than the former. Moreover, the amebal form of B. hominis trophozoites was also detected in the 23 watery fecal specimen and mice ascites specimen. The trophozoites of B. hominis were varying in shape and size depending on their living environment.

Key words: Blastocystis hominis, Trophozoite, Morphology, Pathogenicty