To study the ecological mechanisms underlying the responses of the functional feeding groups and dominant populations of rotifers to environmental factors in a slightly eutrophic lake, zooplankton samples were collected once weekly during July 2011 and June 2012 from Lake Tingtang, located in Wuhu City, Anhui Province, China. We also identified and analyzed annual variations in the density of each functional feeding group, the dominant populations, and the egg ratios of the dominant populations of rotifers. Simultaneously, physicochemical variables of water samples collected from Lake Tingtang, including water temperature, chlorophyll a (Chl-a) concentration, transparency, pH value, TN, NO₃^--N, NH₄⁺-N, TP, and PO₄^3- were measured. The Chl-a concentration in each water sample was measured in two fractions:one filtered through a 25 μm plankton net (Chl-a < 25 μm) and another unfiltered (Chl-a), which were used as biomass indicators of the algae with a smaller volume and all phytoplankton, respectively. On the basis of Pearson correlation and multiple linear regression analyses, the relationships between the densities of each rotifer functional group and dominant population and each of the environmental factors (abiotic factors, such as water temperature, food resources measured by the Chl-a concentrations of the algae with different cell volumes, and biotic variables of potential competitors, such as cladocerans and predators, including copepods and carnivorous Asplanchna rotifers) were analyzed. The main results were as follows. (1) Among the four dominant rotifer species occurring in Lake Tingtang, Polyarthra trigla was considered as a raptorial species, whereas Brachionus diversicornis, Anuraeopsis fissa, and Filinia longiseta were classed together as filter-feeding species. Suckers such as Trichocerca spp. were not considered in the present study because of their extremely low density. (2) Principal component analysis (PCA) showed that water temperature, Chl-a concentration, the densities of cladocerans, copepods and their nauplii, and Asplanchna were crucial for determining the dynamics of rotifer community structure in Lake Tingtang. Water temperature and Chl-a concentration of all phytoplankton was the most important factor shaping the annual dynamics of the filter-feeding and raptorial rotifers in Lake Tingtang, respectively. However, interspecific competition and predation pressure were not the key factors controlling the seasonal dynamics of any functional feeding groups. (3) Interspecific competition and predation pressure were also not the key factors affecting the annual dynamics of dominant populations of filter-feeders. Water temperature and the Chl-a concentration of algae with a smaller volume (Chl-a < 25 μm) were positively correlated with the densities of B. diversicornis and F. longiseta, classified as filter-feeders. Furthermore, the seasonal dynamics of B. diversicornis and F. longiseta were principally controlled by Chl-a < 25 μm. In comparison, the density of A. fissa was only affected by water temperature. (4) The egg ratios of filter-feeding rotifers, including B. diversicornis and F. longiseta, and the raptorial species P. trigla were mostly influenced by water temperature. Additionally, the egg ratios of three rotifers decreased with a decrease in water temperature. Taken together, the results indicate that water temperature and food resources are more likely to be the key factors affecting the annual dynamics of filter-feeding and raptorial rotifers than are the other examined variables, such as interspecific competition and predation pressure.