The fraction of absorbed photosynthetically active radiation (FPAR) is an important parameter to estimate the net primary productivity (NPP) of terrestrial ecosystem by remote sensing.However,when the leaf area index (LAI) and other parameters increase,FPAR becomes less sensitive to NPP at the same time.In order to analyze a more accurate linear relation between NPP and FPAR,some scholars point out a concept in allusion to the absorbed photosynthetically radiation of chlorophyllFPAR absorbed by photosynthetically active vegetation (FPARgreen)which is more accurate and helpful for monitoring and analyzing crops compared with FPAR.Nowadays FPARgreen is extracted by vegetation index inversion,and its final inversion precision is affected by the vegetation index selected.The PROSPECT+SAIL model was used to calculate the true FPARgreen.Various common vegetation indices were stimulated to make linear fitting with the linear fitting precision of each vegetation indices.Some parameters including leaf inclination angle and soil reflectance were modulated to screen the best vegetation index.