Independent measurements of sap flow in stems of Haloxylon ammodendron,Nitraria tangutorum and Calligonum mongolicum and environmental variables using a commercial sap-flow gauges and micrometeorological monitoring system,respectively,were made to study nighttime sap flow activities and its influencing factors,and to estimate the nighttime water consumption for an H.ammodendron stand in an oasis-desert ecotone,located in the middle range of Hexi Corridor,Northwest China.(1)Nighttime sap flow density for these species was high before 0 oclock and decreased quickly,it was weak and fluctuated dramatically between 0 oclock and 6 oclock.We found nighttime sap flow densities between these species were very significant (P<0.01),and the mean value for H.ammodendron,N.tangutorum,and C.mongolicum was 3.73,1.12,and 6.07 g·cm^-2·h^-1,respectively.The results showed that sap flow density of three species all decreased in typical rainy days.(2)The total nighttime water use for these species was close related to the stem diameter during the study period (R²=0.92),and it was not significant difference between different months (H.ammodendron,P>0.05;N.tangutorum,P>0.05;C.mongolicum,P>0.05).We found that H.ammodendron contributed 1% to 30% nighttime water use to daily total water,N.tangutorum contribute 0.1% to 16%,and C.mongolicum conribute 1.5% to 20%,respectively.(3)We presumed that nighttime sap flow for these species were mainly used to refilling because VPD and wind speed only explained 24%,25% and 27% of their variation,respectively.