The fraction of absorbed photosynthetically active radiation (FPAR) is an important biophysical variable, widely used in satellite-based production efficiency models to estimate global primary production(GPP) or net primary production. To the forest, the vegetation canopy is composed primarily of photosynthetically active vegetation (PAV; green leaf) and non-photosynthetic vegetation (NPV; e.g., branches and stems). They absorb photosynthetically active radiation(PAR) from the sun, but only the PAR absorbed by PAV is used for photosynthesis. Remote sensing-driven biogeochemical models that use green FPAR(FPAR_PAV) in estimating GPP are more likely to be consistent with plant photosynthesis processes. However, there are no field and laboratory experiments to measure green FPAR at the canopy level. In this study, a method based on the radiative transfer model was used, and the scattering by arbitrary inclined leaves (SAIL) model was modified to classify forest canopy, and to model the canopy spectral reflectance and the PAR absorbed by PAV and NPV of three deciduous broadleaved forests in different scenarios (varied plant area index and leaf area index). Green FPAR of the canopy was calculated based on the PAR absorbed by PAV and total PAR, and the characteristics of the green FPAR and the relation between green FPAR and two vegetation indices (normalize difference vegetation index [NDVI] and enhanced vegetation index [EVI]) were analyzed. Our results showed that the variation in canopy structure influenced the canopy absorption of PAR, and that green FPAR was related to the plant area index and the ratio of leaf area index to plant area index. In high-coverage forests, the green FPAR was close to the total FPAR of the vegetation canopy(> 80%) and the contribution of NPV to the total FPAR is very low. In contrast, in low-coverage forests or open forests, the difference between green FPAR and the total FPAR was large. Especially when the proportion of the leaf area to plant area low(0.5), the ratio of the green FPAR to the total FPAR was 45.86%. The significant relationships were found between two vegetation index (NDVI and EVI) and green FPAR, but compared with NDVI, EVI was more suitable for describing the variation in the green FPAR.