Due to the spatial non-uniformity of terrestrial surface, the traditional observation means is difficult to extend from point to plane. This paper used SEBAL mode1 witch is based on land surface heat balance and MODIS image data to estimate evapotranspiration and its temporal and spatial distribution characteristics in Tailan River basin located in arid region．The results indicated that the pertinence of daily evapotranspiration of actual observation and that of inversion value is 0.88, and the pertinence monthly is 0.91 that is higher precision. The estimated evapotranspiration in whole year is about 7.04×108 m3 which is 4% greater than that computed by water balance method. According to test of every precision, the results computed by SEBAL model is credible.