The residues of quinolone antibiotics-ofloxacin (OFX), norfloxacin (NOR), ciprofloxacin (CIP) and enrofloxacin (ENR) in Qingshitan Reservoir were detected by high performance liquid chromatography (HPLC). Correlation between the concentrations of antibiotics and physical-chemical properties of water was analyzed, and ecological risk was evaluated by risk quotient method as well. The results showed that the ranges of OFX, NOR, CIP and ENR in Qingshitan Reservoir were 50.00-660.13, 3.70-5.00, 3.49-6.22 and 4.59-6.06 ng/L, which were at the medium level or slightly lower level comparing with the concentrations of antibiotics in domestic rivers. The NOR concentration was significantly correlated with pH and turbidity, and the CIP concentration was significantly correlated with total phosphorus (TP) concentration. While there was no significant correlation between OFX and ENR concentration and all other physicochemical indicators of water. The ecological risk assessment showed that OFX had posed a high risk in the western and eastern areas of Qingshitan Reservoir, while NOR, CIP and ENR were found to pose a moderate risk.