Abstract: In order to explore the nitrogen cycle process in estuarine wetland of plateau lake, the sediments in Luoshijiang estuarine wetland of Erhai Lake was taken as the research object, and the quarterly field investigation involving 8 monitoring sites was conducted to analyze the spatial and temporal distribution of sediment nitrogen. An in-situ incubation approach with top-closed PVC tubes was carried out to study the net mineralization and nitrification rate of sediment nitrogen in summer and autumn. The results showed that: (1) The contents of ammonia nitrogen (NH₄⁺ -N), nitrate nitrogen (NO ₃^--N) and total nitrogen (TN) in Luoshijiang estuarine wetland sediments were 5.92±6.31, 14.49±20.89 and 1 408.98±625.29 mg·kg^-1, respectively. The content of NH₄⁺-N showed a decreasing trend from the inlet to the outlet, and was significantly higher in winter than in others seasons (P<0.05). The contents of NO₃^--N in sediments showed a decreasing trend from the west to the east side of the wetland. There was a significant seasonal difference in NO ₃^--N content (P<0.01), which showed much higher content in spring than in other seasons. (2) The net nitrogen mineralization and nitrification rates in sediments varied from -0.244 to 0.256 and from -0.085 to 0.084 mg·kg^-1·d^-1, respectively. The net nitrogen mineralization rates of both cultivation period and nitrification rate of cultivation period Ⅱ at the inlet of the wetland were significantly lower than that at other monitoring sites (P<0.05). The nitrification rate of cultivation period I was higher in the middle of the wetland. The net nitrogen mineralization rate was greater than the nitrification rate and NH₄⁺-N accumulation was formed. After the cultivation, the inorganic nitrogen mainly existed as NH₄⁺-N in estuarine wetland sediments (i.e., 55.37% of the total amount of NH₄⁺-N and NO₃^--N). (3) Pearson correlation analysis showed that the net nitrogen mineralization rate was significantly negatively correlated with water content (P<0.05). There was a highly significant positive correlation between nitrification rate and NO ₃^--N content before cultivation (P < 0.01), while a negative correlation between nitrification rate and NH4+-N content before cultivation (P < 0.05).