Coordinating the relationship between water resources development and utilization and water resources protection，and promoting harmony between people and water are issues that must be considered in the construction and operation of water conservancy projects.It is of great significance to study the changes of water quality in the reservoir area before and after the operation of Xiajiang water conservancy project.Taking the ammonia nitrogen，permanganate index and total phosphorus in the monitoring sections of the eight water functional zones in the reservoir area as the main analytical indicators，the interaction and variation of these three indicators were investigated from the time and space sequences，and the causes of water quality changes were analyzed.Propose corresponding countermeasures.The results show that the water quality of the water function area（according to two-factor evaluation）in the reservoir area after the operation of the reservoir is generally good，and the basic control is between II and III water.The permanganate index is relatively stable， but has a slow growth trend； ammonia nitrogen and total phosphorus are significantly correlated and have a certain upward trend.