Abstract: 【OBJECTIVE】Fraction of Absorbed Photosynthetically Active Radiation (FPAR) is one of important variables in many productivity and biomass estimation models, therefore, it is significant to retrieve FPAR accurately for the improvement of model precision. 【METHOD】Based on the field experiment of corn, this paper analyzed the correlations between FPAR and spectral reflectance or the differential coefficient, and discussed the regression of FPAR and the typical spectrum bands reflectance or differential coefficient，which was compared with the regression of NDVI, RVI and FPAR. 【RESULTS】The reflectance of visible bands shows much better correlations with FPAR than near-infrared bands. The correlation curve between FPAR and differential coefficient varies more frequently and greatly than the curve of FPAR and reflectance. Reflectance and differential coefficient both have good regressions with FPAR of the typical single band, with the maximum R2 of 0.873 and 0.882, and have better stepwise regressions of multiple bands (R2 is 0.906 and 0.944, individually). In a word, differential coefficient is a little more effective than reflectance for FPAR estimation. However, normalized difference vegetation index (NDVI) and ratio vegetation index (RVI) show the best regression results, compared to reflectance and differential coefficient. 【CONCLUSION】On the whole, the reflectance and differential coefficient have good relationships with FPAR , and could be used for FAPR estimation effectively.

Key words: corn, FPAR, reflectance, differential coefficient, NDVI, RVI