Urban rivers pollution is a serious issue facing the world today. With the controlling progressively for most of the urban point source pollution, endogenous release of nitrogen and phosphorus from sediments, which could continuously pollute river water, became the greatest challenge for the remediation of urban river. The purpose of this study was to examine the spatial and temporal characteristics and risks of nitrogen forms in surface sediments of the river with basin rapid urbanization. Liangtan River, which is a typical urban river and has been greatly polluted due to the rapid development of the city and industry on the basin of wastewater, was selected to carry out a seasonal investigation of nitrogen forms and water environment parameters. The results showed that the range of total nitrogen (TN) concentrations in surface sediment of Liangtan River and its tributary (Huxi River) were 2.63~8.12 g/kg, and contents of the ion exchange nitrogen focusing (IEF-N), weak acid leaching nitrogen (WAEF-N), alkali leaching (SAEF-N) and strong oxidant may leach nitrogen (SOEF-N) contents were 190~1 764, 119~1 139, 208~2 039 and 159~2 829 mg/kg, respectively. The high variability of such N forms was attributed to the distribution pattern of the pollution sources (such as urban, industry, and farming) in the basin. The contents of TN, WAEF-N, SAEF-N and SOEF-N in sediments decreased gradually from the upstream to the downstream of Liangtan River, while the IEF-N with the highest activity showed different peaks in the urban reach, indicated that the spatial distribution of the N forms in river sediments was dominated by the watershed anthropogenic activities and pollution types. Meanwhile, the transferable nitrogen (TF-N) accounted for 52.9%~72.3% in TN, with higher IEF-N percentage in urban reach than these in non-urban reach, showing the higher release risk of N in urban river. Seasonal pattern of the majority N forms in surface sediment of Liangtan River showed the winter were significantly higher than summer. The statistical analysis showed that sediment different N forms parameters had significant correlations with each other, indicating that their closely mutual transformation connection; in addition, the contents of different N forms were significantly and positively associated with pH, DO, and DOC in surface water, indicating that exogenous water pollution hand a positive impact on sediment nitrogen release. Overview, N forms in the surface sediment of Liangtan River showed a great variability in spatial as the results of the pollution sources pattern in the process of urban development. There was a high release risk in the urban reaches due to the small molecular carbon input and higher exogenous pollution loading. The regulation of endogenous nitrogen release was the key point for river management in the future.