To study hydrological features and physical and chemical characteristics of urban stream located in the plain river network area in the process of water resources regulation, and to discuss the forming and composition of nitrogen in urban stream based on water resources regulation. Effects of water regulation on the ammonium release from sediments in urban stream were studied under the condition of experimental simulation. The results showed that diurnal variation of water depth under the action of water resources regulation was significant. The value of DO in the overlying water along the water resources regulation path tended to decrease, while the concentration of permanganate index tended to increase. The concentration of nitrate in overlying water along the water resources regulation path gradually decreased, while the concentration of ammonium significantly increased. DO and permanganate index were the main factors influencing the concentrations of nitrate and ammonium in overlying water. Ammonium released from the sediments was an important source of ammonium in overlying water. Water resources regulation had a significant influence (P < 0. 05) on the concentration of ammonium in overlying water, but had no significant influence on the amount of cumulative ammonium released from sediments (P > 0. 05).