Abstract: PAR (Photo-synthetically Active Radiation) is an important field of the research on global change and terrestrial ecosystem, and is not only an important factor for measuring photosynthesis but also a driving factor of global change. This paper comprehensively reviewed the PAR estimation methods, and included the traditional methods and the remote sensing methods. The climatological and the parameter methods are the most common traditional methods, and the conversion factors and parameters methods based on remote sensing are developed from the traditional methods. The climatological method are a common method for estimating PAR, however, with the development of the study on ecosystems, the methods based on remote sensing become a new kind of methods, which can cover a wide range. Estimation of regional and global PAR by remote sensing becomes possible. How to produce long time series PAR is one of the current concerns around the world. Previous studies have showed that quantitative methods will be the main kind of estimation methods, such as the LUT method. It not only explains the mechanism of PAR in the transmission process, but also enhances the reliability, operability and universality of the estimation methods.

Key words: estimation, influence factors, PAR, remote sensing