To study the ecological status of the Juma River, we conducted a survey of the protozoa in the Bei- jing section of the river during March to November 2004. A total of 310 protozoa species, belonging to 157 genera, were observed, including 134 flagellate species, 64 sarcodina, and 112 ciliate. The most species-rich orders were Euglenoidida (39 species), Kinetoplastida (25 species), Volvocida (21 species), Chrysomonadida (21 species), Hypotrichida (18 species), Scuticociliatida (17 species), and Hymenostomatida (15 species). Cryptomonas ovata was the dominant species, whereas Cinetochilum margaritaceum was subdominant. Jac- card similarity indices among the protozoan communities from the nine sampling stations varied between 0.4569 and 0.5950. After comparing the characteristics of the protozoan communities and the func- tional-trophic groups with those of other waters, we found that the percentage of Phytomastigophora, identity of dominant taxa and the functional-trophic structure of the protozoan communities indicate an oligotrophic to mesotrophic state.