Evapotranspiration is an important part of the energy balance of terrestrial ecosystems and a key link in the atmospheric water cycle. However，due to the limitation of practical conditions，there is a lack of evaluation of the performance and applicability of long-time remote sensing evapotranspiration products of different underlying surface types at the basin scale，resulting in many uncertainties in the estimation of water demand of the basin ecosystem，the evaluation of water resources，and the management and use of water resources. Therefore， based on the long-term time-series flux monitoring data of the ground positioning stations of different ecosystems in the Heihe River Basin，this paper uses the random forest algorithm to construct a multi-site，long-time series， high-precision ground actual evapotranspiration dataset（15 stations，113 station years，daily scale），and selects six commonly used remote sensing evapotranspiration products （SSEBop，GLEAM，MOD16，PML_V2， GLASS and ETMonitor）and extracted the annual values of evapotranspiration products of raster pixels in each ecosystem type site，and evaluated the accuracy and applicability of each remote sensing evapotranspiration prod‐ uct in the Heihe River Basin by R²，RMSE，MAE，Bias and other indicators. The results showed that：（1）SSE‐ Bop products had the highest overall accuracy in the Heihe River Basin（R²=0. 63，RMSE=251. 99 mm·a-1），followed by ETMonitor products（R²=0. 26，RMSE=275. 47 mm·a-1），GLEAM products（R² was not significant）， GLASS products with the smallest Bias were -22. 57 mm，and GLEAM products were the largest（-317. 49 mm）.（2）The performance of the six remote sensing evapotranspiration products in mountain forest system and cropland system was relatively good，and the performance in desert forest system and desert system was the worst，while the actual evapotranspiration of wetland system was generally underestimated. Among them，the SSEBop product was underestimated in all ecological types except the cropland system，while the GLASS product performed well in the desert forest system but seriously overestimated the actual evapotranspiration of the desert system.（3）At the station scale，the ET of wetland ecosystem was the largest，about 1210 mm，and that of desert ecosystem was the smallest，about 180 mm. By evaluating the accuracy and applicability of different re‐ mote sensing evapotranspiration products in the Heihe River Basin，this study provides a scientific basis for the selection of evapotranspiration models in the basin under complex terrain，climate and ecosystem conditions in arid areas，and also provides a reference for the scientific management and use of water resources and ecological protection in the basin.