Abstract: The affected factors and ecological effects of the nitrogen form changes in sediments from Erhai Lake were discussed by studying their characteristics of spatial distribution and seasonal variations. The results indicated that the contents of the total nitrogen (TN) were between 2354and 6174mg/kg, and the spatial distribution showed the whole downward trends in the northern, the southern and the middle regions. The contents of the transferable total nitrogen (TTN) were between 1158and 2921mg/kg and contributed 43% to the TN, and its spatial distribution trends were the same as that of their TN. The decreasing order of the content of different forms of TTN was:SOEF-N (974-2515mg/kg)＞WAEF-N (91-210mg/kg) ＞SAEF-N(38-198mg/kg) ＞IEF-N (66-130mg/kg). The spatial distribution trends of WAEF-N and IEF-N were the same as that of their TN with higher densities in the middle region for SAEF-N and in the south region for SOEF-N. The seasonal variations of the TN and NTN contents were the highest in the summer (July) and that of TTN and their different forms were the highest in the spring (January). The content of different nitrogen forms showed a decreasing trend with the sediment depth increased. The enrichment rate of NTN was higher than that of TN in the surface sediment. The content of TN in the sediments of Erhai Lake was higher than that in the lakes of the middle and the lower regions of the Yangtze. Meanwhile, the surface enrichment of TN was great. The percentage of TTN and IEF-N in the total nitrogen was relatively low, although the releasing risk of nitrogen was high. This,indicated that there was a small amount of the nitrogen released in the sediment of Erhai Lake. The content of different forms of nitrogen showed a significant positive correlation with TOM and a negative correlation with the water depths for the sediments. Moreover, the nitrogen and the organic matter were synchronously precipitated. The exogenous inputs had strong influences on the nitrogen contents, and the distribution of TTN was greatly affected by the activities of aquatic species such as aquatic plants.