Abstract: 【 Objective 】 To study the effects of different reduced-amount nitrogen topdressing application on cotton aboveground dry matter accumulation, distribution and yield. 【 Methods 】 The basal amount of each treatment was the same, and the field conventional nitrogen topdressing amount was taken as the control, 10%, 20%, 30% and 40% of the conventional nitrogen topdressing amount were applied as the reduced nitrogen topdressing treatments to analyze the effects of reduced nitrogen topdressing amount on cotton aboveground dry matter accumulation, distribution and yield. 【 Results 】 The amount of dry matter accumulated in the upper part of cotton field by conventional nitrogen fertilizer application treatment, 10% nitrogen topdressing reduced treatment and 20% nitrogen topdressing reduced treatment were significantly higher than that of 30% nitrogen topdressing reduced treatment and 40% nitrogen topdressing reduced treatment, and the proportion of dry matter distribution in each treatment of reproductive organs in order of size was: 10% nitrogen topdressing reduced treatment > conventional nitrogen topdressing treatment>20% nitrogen topdressing reduced treatment > 30% nitrogen topdressing reduced treatment >40% nitrogen topdressing reduced treatment. There was a significant linear positive correlation between nitrogen fertilizer, cotton dry matter accumulation and seed cotton yield. 【 Conclusion 】 On the basis of conventional field nitrogen application, 10%-20% reduction in the amount of nitrogen fertilizer will not significantly reduce seed cotton yield, and boll number, boll weight and fiber yield of cotton were not significantly affected. A 10% reduction in the amount of nitrogen fertilizer will not significantly reduce the aboveground dry matter accumulation, nor will it affect the increase of the proportion of reproductive organs.