The use of modern phytolith assemblages for the interpretation of fossil phytoliths shows phytolith analysis is an effective method for understanding the grassland vegetation and climate changes. This paper presents firstly a phytolith reference collection and classification system for Nei Mongol grassland, 23 species of grasses were collected from the studied area, and separated into different leaf, glume, awn and so on for diagnostic Poaceae short cell phytolith investigations. 8 phytolith morphotypes were identified. The phytolith morphotypes from the selected species demonstrate that all Pooideae (C 3) subfamily grasses produce rondel form, especially Stipa baicalens ( 85.5% ), S. grandis (89.7%), S. krylovii (90%) and Aneurolepidium chinese (69.1%). Stipa bilobate form is a useful diagnostic type for differentiating the Stipa dominated grassland. Of the short cell phytoliths produced by Agropyron desertorum , about 74.4% of them are keeled rondel. The increase of percentage of the keeled rondel in the soil assemblages would aid in understanding the grassland desertification processes. Cleistogenes squarrosa of Chloridoideae subfamily (C 4) is dominated by panicoid lobate, simple bilobate and saddle forms, and Setaria viridis of Panicoideae subfamily (C 4) is mainly distinguished by panicoid lobate. The percentage of simple bilobate in the soil assemblages would be helpful for understanding the phytolith assemblages produced by Cleistogenes squarrosa dominated grasslands.
