Abstract: The dynamics of nitrogen content and storage in different organs of Calamagrostis angustifolia and Carex lasiocarpa which are dominant vegetation in swamp wetland were determined,and the utilization rate of nitrogen and its nutrient limitation in the region were analyzed.The results showed that the aboveground and underground biomass might be described by p=γ+αt+βt² and p=a₀+b₀t,respectively.The content of total N,NH₄⁺-N and NO₃^--N varied widely with different organs because of the effects of soil water,nutrient content, atmospheric temperature,vegetable feature and selective absorption to nitrogen,etc.The content of NO₃^--N in different organs varied less than that of NH₄⁺-N,and NH₄⁺-N/NO₃^--N was <1.The N:P content less than 14 in two vegetations showed that it was N but not P was the limitation nutrient to the growth of vegetation in this region,moreover,the limitation was less in July than in August.This conclusion was also drawn from the analysis of the NH₄⁺-N and NO₃^--N content in soil.