Abstract: We study the seasonal patterns of carbon fluxes in two desert shrublands of North China , Yulin Station in Shaanxi Province and Tongliao Station in Inner Mongolia Autonomous Region, using the eddy covariance technique, and qualitatively estimate the impact of extreme temperature and water conditions on carbon fluxes. Our findings show that (1) during 2011-2012, the total net ecosystem exchange (NEE) of Yulin and Tongliao were -132.8 and -59.6 gC/m2/yr respectively, indicating that the shrub ecosystem carbon fixation capacity in Yulin was obvious. (2) Extreme water and temperature conditions have significant effects on carbon fluxes, especially extreme water conditions. On an average over the growing period (April-October), the differences of NEE relative to normal conditions at Yulin and Tongliao are 0.51 and 0.26 gC/m2/s in the extreme water condition and 0.17 and 0.20 gC/m2/s in the extreme temperature condition, respectively. (3) In the peak growing period (July-August), the extreme high temperature (above 27 ?C at Yulin and above 29 ?C at Tongliao) effectively inhibits vegetation photosynthesis, decreasing gross primary production (GPP) by 0.37 and 0.53 gC/m2/s respectively, relative to the normal temperature condition.