We investigated the leaf stoma morphology and quantitative characteristics of 29 dicotyledonous plants in the Tibetan Plateau grasslands by means of optical microscope and analyzed the significant difference among stoma index,which provided experimental basis for revealing the mechanism of adaptation to alpine environment and exploring auxiliary classification of stoma.The results showed that:(1) Most stoma randomly arranged on both upper and lower epidermis and stomatal apparatus was irregular type.(2) The average stomatal length(SL) of upper and lower epidermis were 26.20 μm and 25.56 μm,which was smaller,but stomatal density(SD) and stomatal index(SI) were relatively higher.(3) There were significant difference among various families,genera and species on SL,SD and SI.(4)There were significant correlation between six stomatal quantitative characteristics.(5) SL and SD of upper epidermis were significantly associated with families,genera and species.Other stomatal characteristics of lower epidermis except for SI were significant correlated with plant varieties.We came to the conclusion that the distinctive morphology and quantitative characteristics of leaf stoma of dicotyledonous plants in the Tibetan Plateau grasslands reflected the long-term adaptation to alpine environment and quantitative characteristics of stoma had important value in plant auxiliary classification.