AVHRR-NDVI has been widely used for land cover characterization in global and national scales,yet there are few reports on regional scale,and fewer investigations about the potentials of the original bands of NDVI for grassland classification.This paper explores the seasonal dynamics of four grasslands(meadow-steppe,steppe,desert-steppe,and sand-steppe)in Xilingol,Inner Mongolia using1999AVHRR and its NDVI .First,desert could be easily detected due to its low-flat NDVI pattern.Second,Ch3>3180and Ch5>3100in June could be applied to detect sand-steppe from other two grasslands.Third,Ch2>200in August or NDVI_6～8 >1.2is used to differentiate good meadow-steppe from other land covers.The results have less details compared with TM-based classification,but there are still informations for long-term change detection,espe-cially for desertification.More works are needed to verify the potentials and limitations of AVHRR to detect poor meadow-steppe from normal steppe.