Topdress different amount urea on cotton under film-mulching and drip irrigation during the blooming period,the result showed that content of nitrogen of root,leaf,leaf-stem and reproductive organ of cotton with nitrogen treatment were higher than non-treatment,but the increase had no relation with the amount of nitrogen topdressing.The total absorption of nitrogen increased with the amount of nitrogen topdressing,but the proportion of absorption nitrogen during the blooming period to total nitrogen were downtrend.Topdressing nitrogen treatment had no obvious effect to total nitrogen in soil,but it had a stronger effect to alkalined -nitrogen.There had no significant correlation between content nitrogen of cotton organs and total nitrogen and alkalined_nitrogen in soil.The nitrogen utilization efficiency were downtrend with the amount of topdressing increased.