The effect of salinity, drought and salicylic acid on growth and esterase expression of peanut plants were studied. Seeds of peanut were able to germinate even under relatively high concentration of NaCl (157.5 mM) or PEG (25%). In general, seedling growth was less tolerant to salt stress than vegetative growth stage of peanut plants grown in hydroponic culture containing NaCl, vice versa was detected when PEG was used.While the application of 0.1 mM salicylic acid (SA), inhibit peanut seed germination, it improved seedling and vegetative growth parameters under moderate concentration of NaCl (105 mM). Seedling and vegetative growth parameters were significantly reduced by increase the concentrations of PEG. Application of SA improved growth parameters of peanut plants subjected to 10% PEG.In hydroponic culture, peanut was more sensitive to PEG than NaCl where plants wilted in three days under relatively high PEG concentrations. Root of peanut seedlings increased the esterase expression under the influence of moderate salinity (105 mM) and drought (10% PEG) stresses through increase the number and staining intensity of isoenzyme forms.Increase the number of isoenzyme forms and/or staining intensity as an indicator of increased activity of the enzyme was detected when peanut plants were hydroponically grown in solution with relatively high NaCl or PEG. Application of SA increased the number and/or the staining intensity of isoenzyme forms during seedling or vegetative growth in hydroponic culture containing relatively high concentration of NaCl or PEG.