Generally, the two basic study ways to complete the estimate of terrestrial ecosystems evapotranspiration, ground observation and remote sensing simulation have  their own advantages and disadvantages and are complementary to each other. Therefore, how to extend the surface flux (e.g. latent heat flux) from ground observations to large scale (regional and global scale) through combining remote sensing and ground observations has become a scientific focus. In view of this, we review the four aspects of progress based on this research ideas: ① simple empirical regression model; ② surface energy balance methods; ③land surface process model; ④ land data assimilation, and discuss  the main problems currently and possible solutions.