Potato is the third most important staple food crop in terms of consumption, yet it is relatively susceptible to yield loss because of drought. As the first step towards improving drought tolerance in this crop we set out to investigate adverse effects of drought stress and different varieties evaluation of drought tolerance. Two experiments were carried out under greenhouse conditions for PEG-induced water stress. The first experiment aims to determine the most effected concentration from PEG-8000.Thus,seedlings were treated with Polyethylene glycol(PEG-8000) at different concentrations (0%, 10%, 15% and 20%) in two consecutive stages of growth, on three varieties. Phenotypic data (photosynthesis Fv/m and Yield, plant height (cm), leaf number, leaf area ,plant fresh weight, plant dry weight, root length, root fresh weight, root dry weight, number of tubers, a tuber wet weight and tuber dry weight) showed highly reduction under 20% concentration of PEG.