In order to figure out the influence of the water diversion from the Yangtze River Project (WDP) on the rebound of total phosphorus (TP) concentration in Lake Taihu after 2016,this study analyzed the water quantity, phosphorus flux and phosphorus form of Yangtze River and other inflowing rivers including Lake Taihu and Gonghu Bay around 2016 based on the data of water quantity, phosphorus flux transfer from Yangtze River and the phosphorus stock in the lake. The result shows that the average annual phosphorus flux into the lake was 97.56 t and the average annual water inflow volume was 816 million m³ around 2016. From the perspective of water volume, phosphorus flux into the lake, short-term phosphorus response after water diversion and phosphorus increment in each lake area, the correlation between the WDP and the TP rebound in the lake after 2016 is not strong. The cumulative phosphorus flux from the WDP was 877.97 t, accounting for 4.58% of the total TP flux into the lake, and the accumulative amount of lake water accounted for 7.36% of the accumulative amount of lake water in Lake Taihu, the phosphorus flux per unit of water is only about half of that of other water, which accounts for a relatively limited proportion. Compared with the main inflow rivers of Lake Taihu, the water quality from Yangtze River is good. The TP concentration in the inflow rivers is generally higher than the TP concentration of the lake itself. At present, in addition to ensuring the safety of water supply and alleviating the water bloom crisis, the incoming water from the WDP has certain improvement effect when the lake is serious eutrophic. In the next step, we must pay attention to the relationship between the phosphorus flux brought by water diversion and the phosphorus circulation system in Lake Taihu, so as to ensure the ongoing WDP continue to have a positive impact.