MODIS Normalized Difference Vegetation Index(NDVI) has been widely noticed.It has relation with,but is different from NOAA/AVHRR NDVI.Using EOS/MODIS and NOAA/AVHRR data on the same day,the calculation of mean NDVI at county-level is conducted,and the computing method and the results are introduced.The application of the Enhanced Vegetation Index(EVI) in Shaanxi Province is discussed.Results of analysis show that although there is difference between MODIS NDVI and NOAA/AVHRR NDVI,they both can reflect the spatial distribution and the temporal variation of the vegetation.The MODIS EVI is more sensitive to the variation of vegetation conditions and can improve the precision of quantitative analysis,thus having good application potentials.