Abstract: In order to reveal the distribution characteristics of nitrogen in surface sediments of Dongting Lake and its impact on environmental pollution, we studied the distribution characteristics of convertible nitrogen (TTN) and non-convertible nitrogen (NTN) composed of ion exchange nitrogen (IEF-N), weak acid leachable nitrogen (WAEF-N), strong alkali leachable nitrogen (SAEF-N), and strong oxidant leachable nitrogen (SOEF-N) in lake surface sediments using fractional leach method. The main reasons affecting the distribution of nitrogen were analyzed by multivariate statistics. The risk assessment of nitrogen in sediments was carried out via single factor evaluation, bioavailability index evaluation, and Nemerow index evaluation. The results showed that TTN was the main component of nitrogen in the surface sediments of Dongting Lake, and the general distribution of all forms of convertible nitrogen was as follows: WAEF-N > SOEF-N > IEF-N > SAEF-N. NTN and SAEF-N were significantly correlated with TN, indicating that they were most closely related to TN, and had a consistent change trend. A significant correlation was observed between SAEF-N and NTN, indicating that the nitrogen morphology was relatively stable in the sampling area with high TN content. The single factor pollution index and Nemero index evaluated that the nitrogen in the sediments of Dongting Lake was mainly slightly polluted. The evaluation of bioavailability index showed that the nitrogen in sediments was mainly heavily polluted, and some areas were mildly or moderately polluted.