Abstract: 47 species of plants were found in the diet of Black-necked Cranes wintering at Caohai Nature Reserve in southwest China,38 of which were natural plants,9 cultivated plants.Sedges (7 species) are the major food source,accunting for 76.54%,cultivated plants only 2.14%.Underground-tuber is a main fragment type consumed,accounting for 35.14%,most tubers from sedge family.Seeds of Rumes acetosa account for 27.54% total food items of seeds and flowers.The results of an analysis on variance for five main food plant species.suggested that main sources of variance are due to the month rather than duplicate slides.This variation in the diet is significant (F>5.87,df1=4,df2=70).