The spatial and temporal distribution of rotifers, together with various environmental parameters, in Lake Buluntuohai were investigated from autumn of 2006 to summer of 2008, and the relationship between the distribution pattern of rotifers and the environmental parameters was analyzed accordingly.The results showed that 30 taxa were recorded in total and the dominant spe-cies included Polyarthra trigla, Filina longiseta, Hexarthra mira, Brachionus quadridentatus, Keratella quadrata and K.cochlearis.Both the rotifer density and biomass displayed a clear seasonal pattern with two peaks in autumn of 2006 and in summer of 2007.The spatial dynamics of rotifers during the two years were characterized by two distinctive features:The maximums of rotifer density and biomass were recorded in one of the bays in the lake, called Luotuobozi, and the biggest number of species was identi-fied in main water body, the open water in the lake.The density and biomass of rotifer were found to be in a decreasing order from sampling sites in the open water to eastern littoral zone and to western littoral zone.CCA results also showed that certain species, such as Polyarthra trigla were associated with water temperature, dissolved oxygen and the biomass of phytoplankton.The rotifer biomass in the lake was mainly determined by phytoplankton seasonally, while the biomass presents a negative relation with poten-tial predators(cyclopida)and competitors(cladocera)that both dominated the rotifer biomass.