Abstract: 【Objective】 The objective of this study is to study the regulatory effects of different nitrogen fertilizations and densities on the growth and development of cotton in the hope of providing a theoretical basis for rational dense planting and optimal nitrogen application of s Gossypium barbadense L. in the future. 【Methods】 Under the natural ecological conditions in southern Xinjiang, the effects of nitrogen-dense interaction on the growth, development, yield and quality of sea-island cotton were studied by using Xin 78 as the material and a two-factor experimental design, with two planting densities in the main area and four nitrogen application levels in the secondary area. 【Results】 The results showed that the plant height, stem diameter, number of fruit branches and the number of main stem leaves were positively correlated with nitrogen application rate, but negatively correlated with planting density. The SPAD value of leaves increased with the increase of nitrogen application rate and density during the whole growth period. The dynamic curves of dry matter accumulation of Gossypium barbadense L. under different treatments were in line with the logistic model, and the dry matter accumulation of D₂₄N₂ was the largest, reaching 22,462 kg/hm², but the dry matter accumulation and distribution of D₂₀N₀ in the reproductive organs accounted for the largest proportion, reaching 72%. The number of boll per plant and the weight of each boll were positively correlated with nitrogen application rate, and negatively correlated with planting density, but the number of plants harvested per unit area was positively correlated with planting density, and the lint yield and seed cotton yield of D₂₄N₂ combination were the highest, which increased by 2,251.65 kg/hm² and 774.77 kg/hm², respectively compared with the lowest D₂₄N₀ combination. Planting density and nitrogen fertilization rate had no significant effect on the fiber quality of sea-island cotton. 【Conclusion】 Under the planting mode of machine picking cotton in southern Xinjiang, when the planting density is 240,000 plants/hm² and the nitrogen application rate is 320 kg/hm², the growth indexes of sea-island cotton performed well, and the lint yield is the highest, reaching 2,122.62 kg/hm².