The investigation on water quality of Bailianjing reach in Shanghai was carried out from April 2007 to April 2009.One cross-section at South Ferry of Huangpu River and three cross-sections at Bailianjing River were chosen and the survey covered both the spring and neap tides throughout the years.The damming of pump-gateway engineering on Bailianjing River was started in October 2007.Five water quality parameters which were dissolved oxygen (DO) , biochemical oxygen demand (BOD₅) , permanganate index (COD_Mn) , total nitrogen (TN) and total phosphorous (TP) , were used to calculate the standard category index of 4 cross-sections.The results showed that the most important pollutants were TN and TP.Weight coefficients of TN in excess of 40% or even 50%, were over V grade and didn't meet the corresponding water quality standard.Weight coefficients of TP were more than 10% or even 30%, and TP content was 0.8⁵.6 times as high as National Grade IV.In general, water quality of three sites at Bailianjing River was inferior to that of Huangpu River, but the pre-construction water quality was better than building sluiced.Before pump-gateway was constructed, the proportion of IV grade water in Bailianjing River during spring tide period was 29%, 21% above that during neap tide period (8%) .After pump-gateway engineering started, the percentage of the water grade worse than V during spring and neap tide periods was 87% and 88%, showing that tides did not have any noticeable effect on Bailianjing River.