Over the past few decades Miscanthus has been studied as a potential bioenergy crop in Europe but not much been studied in Korea although Korea has many native Miscanthus species and genetic resources. Because of their features, such as low demands of fertilizers and other agrochemicals, high water use efficiency and high productivity, Miscanthus can be cultivated in marginal lands. However, it is not known how Miscanthus can survive in saline soil and what extent Miscanthus can tolerate salt stress, one of main abiotic stresses in reclaimed lands or dry climates. Therefore, this study was conducted to investigate physiological response of Miscanthus species to salt stress and thus to establish a salt stress threshold. Miscanthus sinensis and M. sacchariflorus showed similar responses to salt stress. Chlorophyll contents, photosynthesis and plant growth were all significantly affected by salt stress. Both species were completely killed at > 100 mM NaCl. The GR50 values estimated by non-linear regression analysis with the logistic model were 116.2 mM and 63.1 mM for M. sinensis and M. sacchariflorus, respectively. These GR50 values can be used as their thresholds of salt stress. Further studies will be conducted to screen salt-tolerant Miscanthus genotypes.