Abstract: We described at the present study that the relationship between the protozoan community structure and the nutrition level of Jiuquxi Brook in Wuyi Mountainbased on the PFU (Polyurethane Foam Unit)method. Six sampling locations were investigated in Jiuquxi Brook in Wuyi Mountain in November, 2000. It was found that the water quality in six sampling locations was at Grade I of national standard. 68 species protozoa including 32 species flagellates, 9 species amoebaes and 27 species ciliates were observed. The species, the diversity index and the abundance of the protozoan community in each station of Wuyi Mountain were very low. It can be concluded that the cleaner the water, the less PFU protozoan species exist. However, our data showed that species abundance also depended on the nutrition level of the water body. That is to say, when the nutrition is under certain value, it is generally believed that the cleaner the water, the fewer the PFU protozoan species exist. This conclusion just accords with the relation model of the water quality evaluation and community structure parameters set up by Professors Chen Jian and Shen Yunfen. There is a transition area in a wild field of water quality. Correlative intensity and correlative direction between community structure parameters and comprehensive chemical pollution index are different. In the transition area, the correlation between comprehensive chemical pollution index and diversity index(D), species number at equilibrium (Seq) and time needed to reach 90% Seq(T90%)positive one (negative) to negative one (positive). the positive correlation between heterotrophic index(HI), constant for colonization rate(G)and comprehensive chemical pollution index(P)turns distinctness (undistinctness) to undistinctness (distinctness). In the end, even in the condition of low nutrition level stream, the PFU method could properly reveal the influence of human activity on local aquatic environment.