Abstract: 【 Objective 】 By studying the differences of agronomic traits, nitrogen accumulation and photosynthetic characteristics among different nitrogen-efficiency varieties, the breeding of varieties was optimized to improve nitrogen efficiency and provide reference for rational nitrogen application.【 Method 】Using cotton varieties Xinluzao 32 and Xinluzao 36 as experimental materials, two nitrogen levels of 240 and 360 kg/hm² were set up to study the differences of nitrogen efficiency among different cotton varieties.【 Results 】The results showed that the plant height, stem diameter and number of fruit branches of Xinluzao 32 were higher than those of Xinluzao 36 under both low and high nitrogen conditions, with a difference of 8.34 cm, 2.34 mm and 1.56 sets, respectively.In terms of nitrogen accumulation, the nitrogen content in roots of the two cultivars decreased gradually, but Xinluzao 32's was higher than that of Xinluzao 36. At low nitrogen level, Xinluzao 32 could accumulate more nitrogen in the later stage of stem, contrary to leaf accumulation. At high nitrogen level, the nitrogen accumulation in the later stage of stem was similar, while Xinluzao 32 had high nitrogen content in leaves, and the difference remained above 3.0 g/kg.In terms of photosynthetic characteristics, the net photosynthetic rate and intercellular carbon dioxide concentration of Xinluzao 32 were higher than those of Xinluzao 36, while the transpiration rate was the opposite.【 Conclusion 】At high nitrogen level, the yield of Xinluzao 32 was the highest, which was 4 022.82 kg/hm². Comprehensive analysis showed that the characteristics of different nitrogen-efficiency varieties were different. Especially under low nitrogen conditions, nitrogen-efficient varieties could utilize nitrogen more effectively, ensure yield and increase yield under sufficient nitrogen conditions.