[Objective] The objective of the study is to analyze the variation of peat soil nitrogen under different degradation states in Gahai lake in South Gansu Province and provide scientific basis for peatland ecological restoration and protection in Gahai lake.[Methods] Through field sampling and laboratory analysis, we studied the changes in surface soil nitrogen(0-40 cm) of peat land with degradation.[Results] Except for the undegraded peat land, the total nitrogen content of the other 3 types of degraded peat land was significantly higher in September than that in July, while the soil C/N ratio and soil total nitrogen change in an opposite direction. The change in the content of ammonium nitrogen in soil was the same in July and September. The soil available nitrogen in the 0-20 cm layer was significantly higher in September than that in July, and the 20-40 cm layer(except for moderate degradation) was the opposite. In the whole profile, total soil nitrogen, soil C/N ratio and available nitrogen content were enriched in 20-40 cm layer. Except for moderate degradation, soil ammonium nitrogen was enriched in the 0-20 cm layer.[Conclusion] The total nitrogen content of 4 kinds of degraded soil has obvious temporal variation, indicating that the vegetation plays an important role in the recovery of peatland in Gahai lake.