Field experiments were carried out to study the effects of N application rate on yield,N fertilizer use efficiency and quality of lettuce cultivated in plastic greenhouse.The results showed that vegetable yield,N use fertilizer efficiency and quality could still be ensured even at 20% reduction in N input compared to N 150 kg·hm-2,which was the local farmer habitual usage.Vegetable yield was increased to 5 353 kg·hm-2,N fertilizer use efficiency reached 17.84%,and the net income was up to 12 091 yuan·hm-2 under N 120 kg·hm-2 treatment.In addition,vegetable growth indexes were improved,and nutrient content and soluble sugar content were achieved at the reduced N fertilizer application.There was a positive correlation between nitrate content in leaves of lettuce and N application rate,indicating reduced N application could effectively inhibit the accumulation of nitrate in vegetables.In consideration of yield and economic benefit,it was recommended to apply an optimum nitrogen application rate at N 120 kg·hm-2 for the high nitrogen contents soil under the plastic greenhouse cultivation conditions.