This article take China north part of the Stipa krylovii grass as the object of study, take the eddy covariance as the major technique method, uses the Stipa krylovii grass observation station in 2008 the carbon flux observation data, has discussed the drought influence to the Stipa krylovii grass ecosystem respiration （Reco） , gross primary productivity （GPP） and net ecosystem CO2 exchange （NEE）. The research discovered： The drought is the limit factor to Reco, GPP and the NEE in 2008. In the growth season, In a half hour criterion and date criterion, Reco increases with drought reduces the tendency, presents the obvious correlational dependence, The Reco maximum value will appear from now on the rainfall on July 3, its value is 3.58gCm^-2d^-1 ;In does not consider the temperature in the situation, In a half hour criterion and date criterion, GPP reduces with soil water content （SWC） reduces, presents the obvious correlational dependence, The GPP maximum value appears in July 4, its value is 7.89gCm^-2d^-1 ;Under drought influence, NEE reduces along with SWC assumes weakens the tendency, When moisture content insufficiency, NEE reduces obviously, Rains previous 10 days of NEE mean value for - 0. 33gCm^-2d^-1, Precipitation latter 10 days increase for -2.21gCm^-2d^-1, Finally drops to -0.12gCm^-2d^-1. The drought is the limit factor to ecosystem carbon cycle in the Stipa krylovii grass.%本文以中国北方克氏针茅草原为研究对象，以涡度相关法为主要技术手段，利用克氏针茅草原观测站2008年碳通量观测数据，探讨了干旱对克氏针茅草原生态系统呼吸（Reco）、生态系统总初级生产力（GPP）和生态系统净碳交换（NEE）的影响。研究发现：干旱是克氏针茅草原2008年Reco、GPP和NEE的限制因子。1）在半小时尺度和日尺度上，Reco均随干旱的增加呈降低趋势，呈现出明显的相关关系，Reco最大值出现在降雨过后的7月3日，为3．58gCm^-2d^-1；2）温度适宜时，半小时尺度和日尺度上的GPP均随土壤含水量（SWC）的减小而降低，呈现出明显的正相关关系，GPP最大值出现在7月4日，其值为7．89gCm^-2d^-1；3）在干旱的影响下，NEE随SWC的减小呈减弱趋势，在半小时尺度和日尺度上同样呈现正相关关系，在水分不足时，NEE明显减小，降雨前10天NEE平均值为-0．33gCm^-2d^-1，降水后10天增大为-2．21gCm^-2d^-1，后20天为-2．46gCm^-2d^-1，之后随SWC的降低，NEE开始减小，最后降至一0．12gCm^-2d^-1。干旱通过影响Reco、GPP和NEE进而影响生态系统碳循环，是2008年克氏针茅草原生态系统碳循环的限制因子。
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