In order to provide bases for determining the suitable irrigation amount for cotton fields in Tarim irrigation area of Xinjiang Uygur Autonomous region, a field experiment was conducted. The relationships between the different irrigation amount (8 100, 6 600, 5 100, 3 600 m3/hm2) and cotton yield, the different irrigation amount and soil leakage water amount, the different irrigation amount and total nitrogen (TN) leaching loss amount were studied. The suitable irrigation amount was confirmed considering the economic and environmental benefits according to the analysis of the employing expenses –benefit law. Under this experimental conditions, the results showed that TN leaching loss varied from 3.3 kg/hm2 to 28.4 kg/hm2. The relationship between soil leakage water amount and irrigation amount was linear, soil leakage water amount varied from 672 m3/hm2 to 2 243 m3/hm2. There was quadratic regression correlation between cotton yield and irrigation amount, the maximum yield was 1 765 kg/hm2 when irrigation amount was 6 937 m3/hm2. Therefore, when irrigation amount attained to certain amount, cotton yield decreased while the total nitrogen leaching loss amount increased with the increase of irrigation amount. Optimal irrigation amount of cotton field was 6 651 m3/hm2 considering the economic and environmental benefits under this experimental conditions.