In the present study we evaluated the trophic state of Guanting Reservoir(Beijing part).The results indicated that thewater in Beijing part of Guanting Reservoir had been in eutrophication. According to the data associated with species composition,dominant species, density, biomass and diversity of rotifers, the relationships between rotifer community structure and eutrophica-lion were evaluated. The results indicated that ten key rotifer species far eutrophication appeared regularly and typically in GuantingReservoir, and the dominant rotifer species were Keratella cochlearis and Polyarthra trigla that annual density and biomass wereover 1000ind./L and 1 mg/L, respectively. There was significant positive correlations between water temperature and seasonal dis-tribution of density and biomass of rotifers ( P<0.05).A significant positive correlation was detected between level distribution ofrotifers and status of eutrophication ( P<0.05).However, there was no obvious vertical distribution pattern of rotifer species insample sites of Guanting Reservoir. The level of diversity in rotifer species was not high; however, a significant correlation wasfound between the level of diversity and status of eutrophication. Our results indicated that there was consanguineous correlation be-tween rotifer community structure and eutrophication, and moreover the eutrophication is main reason causing the change of rotifercommunity strncture.