The normalized difference vegetation index（NDVI） is the most widely used vegetation index

which is not only applied into many operational applications

but also is an important parameter for some models.The objective of the study is to evaluate the effect of the red band and near-infrared（NIR） bands on NDVI

which is the function of red and NIR spectral bands

and to explore the relationship between band position and bandwidth of NDVI with the aim of monitoring the biophysical and biochemical parameters of rice.Canopy hyperspectral reflectance data of rice at seven stages were collected by portable spectroradiometer with a spectral range from 350 nm to 2500 nm.Extreme values of rice reflectance spectra in the visional and NIR regions at different stages were identified in order to determine the suitable band center positions for red and NIR bands of NDVI.Through the analysis of hyperspectral reflectance

the spectral bands at 674 nm and 860 nm were selected as red and NIR bands center positions

and for the computation NDVI.Then

the NDVI values were calculated under variable band position and bandwidth from hypersectral data of rice at different stages.Three scenarios were adopted to study the effects of band position and bandwidth on NDVI as follows.The NDVI values were calculated（1） from a constant red band

centered at 674nm with a 10-nm bandwidth

and variable NIR band positions and bandwidths for rice

（2） from a constant NIR band

centered at 860 nm with 10-nm bandwidth

and variable red band positions and bandwidths

（3） from a constant NIR band

centered at 860 nm with a 10-nm bandwidth

and variable red band bandwidths with 674nm

645nm as band center position

respectively.Moreover

the interactions between bandwidth and the central position of red band under the a precision requirement of 99% were analyzed too.The result indicated that band position and bandwidth of NIR channel have no significant influence on the NDVI of rice canopy at different development stages while those of red channel affect NDVI significantly

especially when band position approaches the red minimum（near 670nm）.That means NDVI is more sensitive to band position and bandwidth of red band than those of NIR band.The sensitivity varied with rice development stages.Relative to the middle and later development stages of rice

the NDVI values derived from reflectance data at early development stages are more easily affected by band position.Although NDVI of rice was sensitive to band position

the difference between NDVI values was less affected by band position

therefore

the data sources should be consistent when NDVI was used to study rice.In addition

the NDVI of rice at different developments was essentially affected by proximity of the red and NIR bands to red edge region（690—740 nm）.Under the 1% error of NDVI

the bandwidth of red band becomes narrower when the central position of the band moves towards longer wavelengths at bloom stages

and it reaches its minimum at round 690 nm.Beyond that position

the bandwidth becomes a little wider.However

for early and later development stages

the variation of red bandwidth with central position was more complicated due to the fluctuation of red bandwidth around 648 nm.The research on the effects of band position and bandwidth on NDVI will provide useful information for remote sensing of rice.