A thermal dissipation probe (TDP) was used to measure the sap flow dynamics of Populus alba L.×P.talassica in the agricultural development zones of Karamay during July 1-25, 2012.Soil mositure, total radiation (TR), air temperature, relative humidity, water vapor pressure deficit (VPD) and wind speed were measured at the same time.The results showed that: Diurnal variation of the sap flow displayed a single peaked curve on sunny days, while it displayed a multi-peaked curves on cloudy days.The average value of sap flow was 0.6059 L/h.Sap flow velocity per unit sapwood area was significantly correlated with TR, air temperature, and VPD and was negatively correlated with atmospheric relative humidity.The ranking of correlation coefficients was TR>air temperature>VPD>relative humidity>wind speed.Sapwood area and diameter at breast height (DBH) were significantly correlated (r=0.834), and the sap-flow velocity per unit sapwood area decreased with increasing stem diameter at breast height (DBH).