In this study, the ET in semi-arid Laohahe Basin was estimated based on the surface energy balance system (SEBS) model and NOAA/AVHRR data. The estimated results were then compared with the reference crop evapotranspiration computed combining the FAO-Penman model and crop coefficients. The relationship between the ET and the land cover, Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST) were comprehensively analyzed. The results show that the SEBS model has a good estimation of the ET for the Laohahe Basin. The ET shows a significant temporal and spatial variability. It gets higher values in July and August, and it demonstrates a descending trend in September and October. The ET is much larger in western mountains area than that in middle and eastern plain area. Different kind land covers have different ET values, in which the forest is the largest, and then in turns are cultivated land, thickets and grass. There exist a positive linear correlation between the ET and the NDVI, and a negative linear correlation between the ET and the LST.