Abstract: Using photographic observation data of grassland phenology over the entire growing season and different satellite remote sensing data in Xilinguole of Inner Mongolia, we analyzed statistical relationships between the two datasets. The results showed that MODIS reflectance in visible light band positively correlated (P0.05) with the ground photographic digital number, in which the most significant correlation appeared between MODIS reflectance in 500 m spatial resolution and the ground photographic digital number. Nevertheless, TM/ETM+ reflectance did not significantly correlate (P0.05) with the ground photographic digital number. The positive correlation between MODIS Normalized Difference Vegetation Index (NDVI) and relative greenness index from ground photography (G%) was obviously higher than those between other vegetation indices and greenness indices. Errors between phenological occurrence dates derived from remote sensing and ground photography data were mostly within 7 days. In conclusion, the reliability of remote sensing phenology monitoring by means of ground photography was of crucial for selecting appropriate remote sensing data source and phenological monitoring index.