After the completion of the river network in central urban area of Tianjin, pollution characteristics of nitrogen and phosphate were analyzed and water eutrophication status was assessed based on a field survey from March 2014 to February 2015. The results showed that the river network water was seriously polluted by nitrogen, and slightly contaminated by phosphorus. Ammonia nitrogen (NH₄⁺-N) and orthophosphate (PO₄^3--P) were the mainly form of nitrogen and phosphate, respectively. The temporal and spatial variations of nitrogen and phosphate in the river network water were obvious. The concentrations of nitrogen and phosphate in the upper water were both higher than those in the downstream water. During the study period, the concentrations of nitrogen and phosphate reached the highest level in March, then decreased gradually and dropped to the lowest level in October, and kept at low level in winter. Compared with the water status before the river network completion, the annual mean concentration of NH₄⁺-N, total phosphorus, PO₄^3--P in Haihe River water decreased by 6.5%, 14.7%, 16.4%, and the annual mean concentration of total nitrogen, NH₄⁺-N, nitrate nitrogen, total phosphorus, PO₄^3--P in Jinhe River water dropped by 18.6%, 34.5%, 12.9%, 31.6%, 32.5%, respectively. This showed that nitrogen and phosphate pollution problem of river network water had been obviously improved after the completion of the river network. The results of eutrophication evaluation and characteristic analysis indicated that river network water was in the stage of eutrophication, the algal growth in river network water was limited by phosphorus. The multiple ways including pollutant source control, sewage interception, water environmental capacity increase and ecological water compensation should be used together for eutrophication control.