Using modern irrigation methods such as border irrigation is one way for an optimum usage of water. Potato, for this study, was cultured in a farm located at Kermanshah faculty of agriculture to evaluate the efficiency of border irrigation. The culture potato was the Agria variety and the applied treatment were 50, 75, and 100 percent of potato plant`s water requirement. Tapes were 12 m and the distance of levees was 75cm. Plant`s water requirement was determined by the evaporation pan method and the use of crop coefficient. Comparison of the product performance, efficiency of water consumption, hemispheric wetted volume, and moisture distribution skill were the evaluation indexes. Results showed that maximum product performance related to the 100 percent treatment was 34.455 tons per hectare; it was, for 75 and 50 percent treatments, 25.938 and 19.168 tons per hectare, respectively. Water use efficiency for 100, 75, and 50 percent treatments was 3.59, 3.55, and 3.53 kg of potato tuber for consuming 1m3 of water. Comparing the product performance in SAS software, treatments were classified in different groups; significant difference was observed between them. [F. Ghasemi Sahebi et al. Effect of water stress on potato product in the drip irrigation (T-Tape). International Journal of Agricultural Science, Research and Technology, 2011; 1(2):95-98].