We investigated the effects of nutrient levels on the abundance and diversity of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB), seven surface sediment samples from small reservoirs at different nutrient levels were collected from the eastern, central, and western parts of Huashan watershed in Chuzhou, Anhui Province to determine the abundance and community composition of AOA and AOB. The results showed that the abundance of bacterial amoA gene (1.85×10⁷ to 2.86×108 g/dry sediment) was higher than that of archaeal amoA gene (1.25×10⁵ to 1.23×10⁶ g/dry sediment) in all sediment samples. The abundance of the archaeal amoA gene exhibited significant positive correlations with total nitrogen concentrations, whereas the abundance of bacterial amoA gene showed significantly negative correlation with pH. Archaeal amoA gene sequences included Nitrososphaera and Nitrosopumilus clusters and the majority of Nitrosospira and Nitrosomonas oligotropha lineages.