Increasing of people population and demanding for agricultural production result in water shortage that is one of the biggest problems at agricultural and food production sectors. The fat after the carbohydrates is in the second category of importance. Sunflower is a remarkable oil source in the world and particular in Iran. Water and nitrogen are both important in crop production. One of the methods for water saving in Iran is determination of the optimum irrigation requirement of strategical productions that grows up plant productions per unit volume of water consumption. The objective of this study was two quantify the response of the two sunflower hybrids to variable irrigation and N fertilizer application via drip (T-tape) irrigation system with fertigation management to determine the optimum amount of N fertilizer as a function of irrigation. This study was conducted in 2010 at the Isfahan university of thechnology research field in Lavark (lat:32? 98" north and long:49? 57" east), which is located in Najaf Abad city. The experimental treatments consisted of four levels of irrigation, inclouding two deficit irrigation levels 0.6 SMD (soil moisture depletion) (referd as W1), 0.8 SMD (referd as W2), a full irrigation level, 1 SMD (referd as W3), and an over irrigation level 1.2 SMD (referd as W4) and three N fertilizer levels inclouding 0 kgN/ha (N0), 50 kgN/ha (N50) and 100 kgN/ha (N100). The treatments were arranged in a strip-plot statistical design with randomized complete blocks and three replications. The two sunflower hybrids euoroflor and sirna was planted on june 2 in 2010. The result indicated that the plant height, stem diameter, total biomass, grain production, oil production, irrigation water use efficiency (IWUE) of grain and irrigation water use efficiency of oil were affected by irrigation (P 0.05) for two hybrids and also affected by N fertilizer (P 0.05) for two hybrids. Also the diameter of floor, stem diameter, biomass, grain production, oil production, thousand grain weights, irrigation water use efficiency of grain and irrigation water use efficiency of oil were affected by the intraction between irrigation and nitrogen fertilizer (P 0.05). The diameter of floor and thousand grain weights were affected by irrigation (P 0.05) for two hybrids, however were not affected by N fertilizer. For both hybrids the optimum level of irrigation was the W3 (1 SMD) with 672 mm water per season to obtain higher IWUE. For the optimum irrigation level, the optimum N rate was 100 kgN/ha (N100) for two hybrids. The maximum value of grain and oil production was occurred for the combination of 672 mm irrigation, W3 (1 SMD), and 100 kgN/ha for euoroflor hybrid and for the combination of 800 mm irrigation, W4 (1.2 SMD), and 100 kgN/ha for sirna hybrid. The negative impact of N fertilizer was showed on grain and oil production for W1 and W2 levels. Also increasing the amount of N fertilizer is not a sound strategy under water stress condition.