The anthropogenic input of nutrients to rivers is the main cause of eutrophication, and both the excessive control and engineering of river channels further complicate the issue. To meet the demand for energy and water resources, thousands of dams, weirs, and sluices have been constructed and affected almost every river, which deeply interferes with the biogeochemistry cycles of nutrients and the ecological function of river systems. Previous research has investigated the ecological effects of eutrophication caused by phosphorus in dammed rivers, since phosphorus limitation of primary production is more predominant in river systems. Dammed rivers can reduce outflow and, hence, sequester a significant amount of phosphorus within the impoundments. As a consequence, river water becomes eutrophic, and the ratios of main nutrients change drastically, owing to the different responses of the nutrients to retention by dams. In addition, sediments in the dammed rivers, which containing high contents of phosphorus, can easily become a potential pollution source, especially under intensive scouring events. At the same time, the abundance of algae communities increases, as certain species bloom in the water column, which aggravates the ecologic effects of river eutrophication and threatens the biodiversity of river systems. Therefore, researchers have found that an efficient management strategy based on annual rainfall storage and dam discharge control can be used to improve the ecological effects of eutrophication in dammed rivers. However, as anthropogenic impacts continue to increase, further studies of dammed rivers are needed to clarify the relationship between artificial control in rivers and river eutrophication, in order to reduce the ecological effects of eutrophication, as well as to quantify the threshold of phosphorus, in order to further understand the eutrophication mechanisms of dammed rivers and the combined effects of nitrogen and carbon, to manage phosphorus within sediments, in order to prevent its release and resuspension, and to address concerns regarding the construction and restoration of landscape rivers with dams throughout China.