Abstract: This paper dealt with the litter of two dominant species Deyeuxia angustifolia and Carex lasiocarpa in swamp of Sanjiang Plain,and analyzed the seasonal variation and content feature of nitrogen in litter and its roles on maintaining matter equilibrium in ecosystems.The nitrogen content in litter decreased with the increasing temperature and aboveground biomass.The weightlessness rate of litter increased with time,and the annual accumulative weightlessness rates of D.angustifolia and C.lasiocarpa were 32.2% and 27.7%,respectively.The annual accumulative nitrogen input amount of D.angustifolia community was 1478mg穖^-2, C.lasiocarpa 587mg穖^-2,while the annual accumulative nitrogen output amount in litter of D.angustifolia community was 759mg穖^-2, C.lasiocarpa 410mg穖^-2.It was suggested that the nitrogen input amount was higher than output,and that the state of nitrogen accumulation was beneficial to the stability of the ecosystems.