Abstract: 【Objective】 To study the effects of different planting densities and nitrogen application amounts on the morphological index and yield of 76 cm equal-spaced cotton roots. 【Method】 The split-zone design was adopted, which was divided into the main zone density (M₁: 225,000 plants/hm², M₂: 180,000 plants/hm², M₃: 135,000 plants/hm²) and the sub-zone nitrogen fertilizer (N₁: 0 kg/hm², N₂: 300 kg/hm², N₃: 600 kg/hm²). 【Result】 The results showed that the yield of seed cotton increased significantly by 10.6%-14.5% with nitrogen application rate of 300 kg/hm².However, when the nitrogen application rate was too high (600 kg/hm²), the dry matter accumulation would decrease.Appropriate increase of planting densities and nitrogen application rates could promote cotton root weight density, root length density, root surface area density, root volume and average root diameter.The root mass and root volume of the highest treatment M₁N₂ (225,000 plants/hm²,300 kg/hm²) were 34.3% and 50.1% higher than those of the lowest treatment M₃N₃ (135,000 plants/hm²,600 kg/hm²), respectively, and the average root diameter and average root surface area were 36.1% and 56.2% higher than those of the lowest treatment M₃N₃ (135,000 plants/hm²· 300kg/hm²), respectively.The root length density was the highest under M₁N₃ (225,000 plants/hm², 600 kg/hm²), which was 20.8% higher than that under the lowest treatment.The final best combination with high yield was M₂M₂ (180,000 plants/hm²,300 kg/hm²), which was 18.5% higher than that of the lowest combination M₂N₃ (180,000 plants/hm²,600 kg/hm²). 【Conclusion】 It can be seen that the planting density of 180,000 plants/hm² and the nitrogen application rate (pure nitrogen) of 600 kg/hm² can promote the yield improvement and root formation in the machine-picked cotton planting mode with an equal row spacing of 76 cm in southern Xinjiang.