Abstract:A thermal dissipation probe (TDP) was used to measure the sapflow dynamics of Platycladus orientali in Ansai County on the Loess Plateau of China from April to October, 2008. Soil water content, photosynthetic active radiation (PAR), air temperature, relative air humidity, water vapor pressure deficit (VPD) and wind speed were measured at the same time. The results showed that patterns of diurnal variation of P. orientalis sapflow velocity on sunny days were similar with a clear pulse creating a single\|peak curve; in the case of restricted soil water levels, the daily average sapflow velocity tended to decline over time so that it was greatest in April and the least in October, being 0.00135 and 0.00011cm·s-1, respectively; sapflow velocity showed a significant positive correlation with PAR, air temperature, and water VPD, and had a negative correlation with the relative humidity, the correlation coefficients being in the order PAR > VPD > Temperature > relative humidity, so that these linear expressions can be used to estimate it; the sapwood area of P. orientali and the diameter at ground level were used for an index relationship to obtain an estimate of sapwood in the sample plots, which was 4.65 m2. Finally, it can be used to estimate the total water consumption used for transpiration by the P. orientali plantation in the growing season of April\| October, which was 1159.6 t·hm-2.