Using Fagopyrum esculentum（Pingqiao NO.2）and Fagopyrum tataricum（Qianku NO.2）as experimental materials to study the effect of NaCl and iso-osmotic PEG on roots vigor, plasma membrane permeability, MDA content and net photosynthetic rate of buckwheat. Under lower concentration salt treatment, roots vigor of two buckwheat varieties obviously increased and Fagopyrum tataricum increased more than that of Fagopyrum esculentum. Plasma membrane permeability and MDA content of roots and leaves in Fagopyrum esculentum and net photosynthetic rate of leaves in Fagopyrum tataricum all obviously increased. Under higher concentration salt treatment, roots vigor of two buckwheat varieties also remained high level. Plasma membrane permeability and MDA content of roots and leaves in Fagopyrum esculentum increased obviously more than that in Fagopyrum tataricum. Net photosynthetic rate of leaves in Fagopyrum esculentum under higher concentration salt treatment obviously decreased and decreased more than that under iso-osmotic PEG treatment, while that in Fagopyrum tataricum showed no obviously difference with control. It indicated that plasma membrane permeability, MDA content and net photosynthetic rate were sensitive physiological indexes of stress resistance in buckwheat and the stress resistance of Fagopyrum tataricum was more than that of Fagopyrum esculentum.