Abstract: This paper analyzes the relationship between MODIS-NDVI and AVHRR-NDVI of the same region at different time, based on Histogram and Feather Space methods. The results show that their shapes are the same, but MODIS NDVIs have more sensitivity to vegetation, and the range of their values is wider than that of NOAA-AVHRR. They have no strong correlations. It is not a good idea to use AVHRR NDVI directly as MODIS history NDVI.