The effects of nitrogen fertilizer reduction and amino acid application on cotton growth，nutrient absorption，yield composition and nitrogen use efficiency in Xinjiang cotton field were studied to provide scientific basis for rational application of nitrogen fertilizer in Xinjiang cotton field. The field experiment method was used to set up no nitrogen fertilizer control(0%N)，nitrogen fertilizer application rate of farmers(130%N)，recommended nitrogen fertilizer application rate of soil testing formula(100%N)，nitrogen fertilizer reduction(70%N)and nitrogen fertilizer reduction with amino acid application(70%N+AA). The plant biomass，nutrient uptake of each organ and seed cotton yield were measured，and the nitrogen use efficiency of cotton field was calculated. The results showed that:(1)The biomass of cotton organs decreased with the decrease of nitrogen application rate；compared with nitrogen fertilizer reduction treatment，amino acid addition significantly increased cotton plant biomass. (2)The nitrogen content of cotton organs decreased with the decrease of nitrogen application rate，or increased first and then decreased. Compared with nitrogen fertilizer reduction treatment，amino acid addition significantly increased the nitrogen content of cotton leaves and flocs. (3)The nitrogen uptake of cotton decreased with the decrease of nitrogen application rate；compared with nitrogen fertilizer reduction treatment，amino acid addition significantly increased cotton nitrogen uptake. (4)Compared with nitrogen fertilizer reduction treatment(6679.48 kg/hm²)，amino acid addition significantly increased the seed cotton yield of cotton，reaching 8230.44 kg/hm² at 70% N+AA treatment. (5)The nitrogen use efficiency of cotton field increased first and then decreased with the decrease of nitrogen application rate，and the highest was 39.65% at 100% N treatment. Compared with the nitrogen fertilizer reduction treatment(18.19%)，amino acid addition increased the nitrogen use efficiency of cotton fields，reaching 49.13% at 70%N+AA treatment. In summary，the combined application of amino acids improved cotton yield and nitrogen use efficiency under the condition of lower chemical nitrogen fertilizer application rate，which could be used as an effective measure to reduce nitrogen fertilizer application and increase efficiency in Xinjiang cotton field.