In order to study the effect of irrigation management on tobacco yield in comparison with nonirrigated condition,an experiment was conducted at Guilan Tobacco Research Station in 2003 growing season. A randomized block design with five treatments and three replications was conducted using 40%, 80% and 100% of available water and nonirrigated (dryland farming) as control. The soil moisture content of different levels was measured by pressure plate and then soil moisture characteristic curve was drived. The soil moisture content was determined with gypsum blocks which had been buried in soil at 15 and 30 centimeters depth. The amount of irrigated water was measured by water gage with 0.1 litter sensitivity. After transplanting tobacco plants, the soil moisture content was measured and irrigation started immediately.The following irrigation period was determind using gypsum blocks and soil moisture characteristic curve. The results showed that irrigation treatments in comparison with nonirrigated control was significant with 1% in fresh leaf, dry leaf yield, price of unit weight and pure income of tobacco farming. The treatment of 40% of field capacity moisture was the best in fresh leaf and dry leaf yield, price of unit weight and unpure income of tobacco farming, having 23050 kg, 3383 kg, 8768 rials and 29553193 rials per hectare respectively. The nonirrigated treatment with 4982 kg, 935 kg, 3800 rials and 3595566 rials was the lowest in comparison with the other treatments.