Based on long-term water quality monitoring data,the indices of water quality identification were applied to evaluate the water quality of Yuncheng Section of the Fenhe River during the period of 2005—2009.The surface water quality of monitoring sites at Xinjiang Station and Hejin Bridge was further classified based on the evaluation.The evaluation results show that COD,BOD5,and ammonia nitrogen exceeded the standard rates substantially,and ammonia nitrogen was the most severe pollution indicator.The results also show that the water quality did not meet the corresponding functional requirements of the water environment,nor did it meet the standards for surface water quality.Water quality controls on COD,BOD5,and ammonia nitrogen should be carried out more strictly.The findings of this work will provide basis for planning,management and protection of Yuncheng City's surface water resources.