This article examined 20 species of grasshoppers, belonging to six families, in Guandaushi forest ecosystem by studying the food plants and the morphology of their mandible, among which, three species are still under further identification. Based on SEM observations, the mandibles of them could be grouped into three types corresponding to their food plant: type 1 forb-feeding, the mandible with inc is or surface consists of sharp dents, and the molar area is a deep, central concavity surrounded by short ridges; type 2 grass-feeding, the incisor surface is somewhat smooth without dents, and the molar surface has long parallel grinding ridges without central concavity; type 3 obligate-feeding, the incisor is blunt, and the molar consists of ridges with a central concavity shorter than type 1. Among the 20 species of grasshoppers in Guadaushi forest ecosystem, the ones belonging to type 1 are Traulia ornata ornata Shiraki, 1910, Xenocatantops humilis (Seville, 1839) and Coptacra sp. 3 of Catantopidae; Atractomorpha sinensis I. Bolivar, 1905 of Pygomorphidae and Erianthella formosana (Shiraki, 1910) of Eumastacidae. The species belonging to type 2 are Oxya podisma Karny, 1915, Oxyrrhepes obtuse (De Haan, 1842) of Catantopidae; Phlaeoba albonema Zheng, 1981, Phlaeoba formosana Shiraki, 1910, and Phlaeoba sinensis I. Bol., 1914of Acridae; Formosacris koshunensis (Shiraki, 1910) and Dnopherula svenhedini (Sjöstedt, 1933) of Arcypteridae and Pternoscirta sauteri (Karny, 1915), Heteropternis respondens (Walker, 1859) and Trilophidia annulata (Thunberg, 1815) of Oeipodidae. Type 3 grasshoppers are Stenocatantops splendens (Thunb., 1815), Parapodisma sp. 1, Parapodisma sp. 2, Sinopodisma kodamae (Shiraki, 1910), and Sinopodisma formosana (Shiraki, 1910) of Catantopidae.