Evapotranspiration is considered a crucial part of the hydrological cycle and surface energy balance. It is regarded as indispensable for effective water resource management, drought monitoring, and agricultural production optimization. Based on the Landsat8 remote sensing data and combined with the surface energy balance system (SEBS) model, the daily evaporation in the basin on six dates in 2019 was estimated and verified. By analyzing the spatiotemporal variation trend and influencing factors of evapotranspiration, the obtained results show that the goodness of fit R² between the actual daily evapotranspiration estimated by the SEBS model, the potential evapotranspiration estimated by the Penman-Monteith (P-M) formula, and the evapotranspiration actually observed in the evaporation dish of the meteorological station are 0.84 (P < 0.01) and 0.602 (P < 0.05), respectively. It has been verified that the SEBS model has high accuracy and reliability in the estimation of evapotranspiration in the Hongjiannao River Basin. The daily evapotranspiration in the Hongjiannao River Basin shows obvious seasonal differences, with the highest in summer, followed by spring, then autumn, and the lowest in winter. The evapotranspiration in the Hongjiannao water body in the eastern part of the basin and in the Chagannaoer and its surrounding areas in the western part of the basin is relatively high. The evapotranspiration in the middle of the basin is relatively low. Among different types of land use, the evapotranspiration of water bodies is the highest, followed by forest land, cultivated land, construction land and grassland, and the lowest is unused land. Among meteorological factors, temperature, air pressure and sunshine duration are the main influencing factors, which are significantly positively correlated with evapotranspiration (r=0.847, P < 0.05), negatively correlated with (r = -0.840, P < 0.05) and positively correlated with (r = 0.801, P < 0.05) respectively, while relative humidity and wind speed have relatively weak correlations with evapotranspiration.