Abstract: The morphology of Chroomonas caudata Geitler collected from Wuxi,Jiangsu Province was investigated by light microscopy and scanning electron microscopy(SEM).The SEM demonstrated that the cell apex of C.caudata has a concave mouth which is anopening of Gullet.The cellular surface of C.caudata possesses many small rectangularplates,longitudinal oblique row arranged from left to right.The perpheral trichocystsare located beneath the two corners of the anterior facing edge of each rectangular plate.Some species of Chroomonas was examined by the SEM,the shape and arrangment ofplates,and trichocysts display similar structure.